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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Mg(CO3)2 by Materials Project

Mg(CO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in an octahedral geometry to six O atoms. There are a spread of Mg–O bond distances ranging from 2.03–2.15 Å. In the second Mg site, Mg is bonded in a distorted octahedral geometry to six O atoms. There are a spread of Mg–O bond distances ranging from 2.06–2.18 Å. There are two inequivalent C sites. In the first C site, C is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.27 Å) and two longer (1.28 Å) C–O bond length. In the second C site, C is bonded in a trigonal planar geometry to three O atoms. There is one shorter (1.26 Å) and two longer (1.29 Å) C–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to one Mg and one C atom. In the second O site, O is bonded in a linear geometry to one Mg and one C atom. In the third O site, O is bonded in a linear geometry to one Mg and one C atom. In the fourth O site, O is bonded in an L-shaped geometry to one Mg and one C atom. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to one Mg and one C atom. In the sixth O site, O is bonded in an L-shaped geometry to one Mg and one C atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Thermodynamic Modeling of the Al-Ce-Cu-Mg-Si System and Its Application to Aluminum-Cerium Alloy Design

Recently discovered AlCe alloys have shown promise in a number of applications, but the propensity of Ce to react with Al and other alloying elements can complicate the phase equilibria and design approach. To solve this, the CALPHAD method is used to explore an alloy within the quinary Al-Ce-Cu-Mg-Si system by developing a thermodynamic database with self-consistent parameters. The database includes a description of all 10 binary systems and 8 ternary systems consisting of: (i) 6 Al-containing ternaries (Al-Ce-Cu, Al-Ce-Mg, Al-Ce-Si, Al-Cu-Mg, Al-Cu-Si and Al-Mg-Si); and (ii) 2 additional ternaries that include Mg and Si (i.e., Ce-Mg-Si and Cu-Mg-Si). The thermodynamic description for the Al-Ce-Mg and Al-Mg-Si systems were reassessed to ensure consistency with the binary systems and the Ce-Mg-Si system is presented for the first time and compared to theoretical data from DFT (Density Functional Theory). In addition to the ternary interactions, the quaternary compound Al3Cu2Mg9Si7 and solid solution extending from the ternary Al2CuMg phase (Al,Si)2CuMg are incorporated. The CALPHAD method is employed and leveraged through the use of a Materials Design Simulator (MDS) to accelerate the design of novel aluminum-cerium-based alloys. The combination of a CALPHAD-based framework with experimental efforts and industrial insight permits the development of three new Al-Ce alloys: Al-3.5Ce-0.4Mg-7Si (Ce-modified A356), Al-5Ce-1Cu-0.5Mg-10Si and Al-19Ce-0.9Mg-1.1Si.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(GaO2)2 by Materials Project

MgGa2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are twelve inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There is three shorter (1.97 Å) and one longer (2.00 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Mg–O bond distances ranging from 1.96–1.99 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three GaO4 tetrahedra, and edges with six GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.09 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five GaO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.09 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.08 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.10 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent GaO6 octahedra. There are four shorter (2.06 Å) and two longer (2.09 Å) Mg–O bond lengths. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.09 Å. In the ninth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent GaO6 octahedra. There are four shorter (2.06 Å) and two longer (2.09 Å) Mg–O bond lengths. In the tenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.06–2.09 Å. In the eleventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four GaO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.09 Å. In the twelfth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.10 Å. There are eighteen inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of Ga–O bond distances ranging from 1.89–1.96 Å. In the second Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine GaO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Ga–O bond distances ranging from 1.90–1.96 Å. In the third Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.09 Å. In the fourth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 55–57°. There is two shorter (1.87 Å) and two longer (1.91 Å) Ga–O bond length. In the fifth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with three MgO4 tetrahedra, corners with three GaO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.08 Å. In the sixth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five GaO4 tetrahedra, edges with three MgO6 octahedra, and edges with three GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.09 Å. In the seventh Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent GaO4 tetrahedra, edges with two MgO6 octahedra, and edges with four GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.08 Å. In the eighth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Ga–O bond distances ranging from 1.88–1.95 Å. In the ninth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is two shorter (1.88 Å) and two longer (1.93 Å) Ga–O bond length. In the tenth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is two shorter (1.88 Å) and two longer (1.93 Å) Ga–O bond length. In the eleventh Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is two shorter (1.88 Å) and two longer (1.93 Å) Ga–O bond length. In the twelfth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six GaO4 tetrahedra, edges with two equivalent GaO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.99–2.05 Å. In the thirteenth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 55–57°. There are a spread of Ga–O bond distances ranging from 1.88–1.93 Å. In the fourteenth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is two shorter (1.88 Å) and two longer (1.93 Å) Ga–O bond length. In the fifteenth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six GaO4 tetrahedra, edges with two equivalent GaO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.99–2.05 Å. In the sixteenth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with six GaO4 tetrahedra, edges with two equivalent GaO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.99–2.05 Å. In the seventeenth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with six MgO6 octahedra and corners with six GaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–57°. There is two shorter (1.88 Å) and two longer (1.93 Å) Ga–O bond length. In the eighteenth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four GaO4 tetrahedra, edges with three MgO6 octahedra, and edges with three GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.96–2.06 Å. There are thirty-six inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form a mixture of distorted corner and edge-sharing OMgGa3 trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form a mixture of distorted corner and edge-sharing OMgGa3 trigonal pyramids. In the third O2- site, O2- is bonded to four Ga3+ atoms to form a mixture of distorted corner and edge-sharing OGa4 trigonal pyramids. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the fifth O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form distorted OMgGa3 trigonal pyramids that share corners with three OMgGa3 trigonal pyramids and edges with three OGa4 trigonal pyramids. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Ga3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Ga3+ atoms to form distorted edge-sharing OMgGa3 trigonal pyramids. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the ninth O2- site, O2- is bonded to four Ga3+ atoms to form a mixture of distorted corner and edge-sharing OGa4 trigonal pyramids. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two equivalent Ga3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the fourteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the eighteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ga3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Ga3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like g

36 MATERIALS SCIENCE↗
DOE OSTI2026

The Effects of Iron and Manganese Doping on the Carbonation of Brucite [Mg(OH) 2 ]

Brucite [Mg(OH) 2 ] is a promising sorbent for carbon dioxide removal (CDR) due to its availability and low calcination temperatures. However, natural and synthetic brucites tend to contain metal impurities, such as iron or manganese, and how these impurities affect the interfacial chemical reactivity is uncertain. Here, in this study, the impact of low concentrations of iron and manganese impurities on the carbonation efficiency of Mg(OH) 2 was examined. Mg(OH) 2 with small amounts (1–5 mol %) of Fe and Mn was synthesized. The increasing substitution of Fe into Mg(OH) 2 was accompanied by the oxidation of Fe. The phase transformation sequence during the carbonation was found to be brucite [Mg(OH) 2 ] → amorphous magnesium carbonate (MgCO 3 ·nH 2 O) → nesquehonite (MgCO 3 ·3H 2 O), regardless of impurity concentration. Both the Fe- and Mn-doped Mg(OH) 2 samples were more reactive than endmember Mg(OH) 2 , possibly due to their higher surface areas and lower stabilities. During carbonation, 3 mol % Fe- and Mn-doped Mg(OH) 2 showed the highest reactivity. The variance in reactivity for Mn-doped Mg(OH) 2 was less than that of Fe-doped Mg(OH) 2 . These results suggest that natural or industrial waste Mg(OH) 2 with less than 5 mol % Fe and Mn impurities may be targeted as more effective CDR sorbents than endmember Mg(OH) 2 .

Carbon dioxide removal↗
DOE OSTI2020

Materials Data on Mg by Materials Project

Mg is alpha La structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. There are six shorter (3.17 Å) and six longer (3.20 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to twelve Mg atoms to form a mixture of corner, edge, and face-sharing MgMg12 cuboctahedra. All Mg–Mg bond lengths are 3.20 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg by Materials Project

Mg is alpha Samarium structured and crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, face, and corner-sharing MgMg12 cuboctahedra. There are six shorter (3.15 Å) and six longer (3.21 Å) Mg–Mg bond lengths. In the second Mg site, Mg is bonded to twelve Mg atoms to form a mixture of edge, face, and corner-sharing MgMg12 cuboctahedra. There are three shorter (3.15 Å) and six longer (3.21 Å) Mg–Mg bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Mechanical properties and strengthening mechanisms of cold sprayed Al-Mg alloys

This paper investigates the mechanical properties and strengthening mechanisms of cold sprayed Al-Mg alloys as a function of Mg content. Cold spray (CS) is a solid-state deposition process that can be used as a repair technique for structural components. However, the limited ductility of cold sprayed materials is an unsettled issue in CS community. Herein, reproducible, and significantly increased elongation to failure (∼15%) in as-deposited conditions is reported in CS Al-Mg binary alloys with low Mg content (≤ 2.5 wt%). Furthermore, reducing Mg content down to 2.5 wt% in CS Al-Mg binary alloys demonstrated comparable mechanical strength to its wrought counterparts. Strengthening mechanisms were analyzed in wrought and CS Al-Mg alloys based upon microstructural characteristics, such as grain size, Mg solute concentration, and dislocation density. A quantitative evaluation of yield strength revealed that grain boundary strengthening is predominant in CS Al-Mg alloys as compared with their wrought counterparts. When comparing among CS Al-Mg binary alloys of different compositions, Mg solute concentration, and dislocation density governed mechanical strength. In conclusion, the underlying mechanism for the variation of mechanical properties and strengthening mechanisms is discussed in terms of these microstructural characteristics.

Additive manufacturing↗
DOE OSTI2021

Evidence of formation of an amorphous magnesium silicate (AMS) phase during alkali activation of (Na-Mg) aluminosilicate glasses

Highlights: • No hydrotalcite-group phase is formed as Al preferentially incorporates into zeolites. • Mg forms an amorphous Mg silicate (AMS) phase. • AMS is a more depolymerized phase when compared to Mg silicate hydrate (M-S-H). • High charge density of Mg effectively stabilizes depolymerized silicates in AMS phase. • Existence of AMS phase should be considered as possibility in Mg-rich AAMs. There is some ambiguity regarding the fate of Mg during the alkali activation of Mg-rich precursors within the broader field of alkali activated materials (AAMs). The present work addresses this issue by studying the reaction products in AAMs synthesized from (Na-Mg) aluminosilicate glasses. Here, instead of magnesium silicate hydrate (M-S-H) phase, Mg exclusively forms an amorphous magnesium silicate (AMS) phase. Compared to M-S-H, AMS is a more depolymerized phase, which has not previously been well documented. The formation of AMS seems to be driven by the high charge density of the Mg cation which effectively stabilizes the depolymerized silicate species. We also show that the lack of hydrotalcite-group phases is due to aluminum depletion by zeolite formation. This work highlights the need to consider the existence of the AMS phase in Mg-containing AAMs, especially in complex systems, where its identification may be difficult.

36 MATERIALS SCIENCE↗
DOE OSTI2022

New insights into Mn 2+ and Mg 2+ inhibition of calcite growth

Impurity ion and isotope partitioning into carbonate minerals provide a window into the molecular processes occurring at the fluid-mineral interface during crystal growth. Here, we employ calcium isotope fractionation together with process-based modeling to elucidate the mechanisms by which two divalent cations with starkly contrasting compatibility, magnesium and manganese, inhibit calcite growth and incorporate into the mineral lattice. Calcite growth inhibition by Mg 2+ is log-linear and K Mg is on the order of 0.02–0.03 throughout the range of {Mg 2+ }/{Ca 2+ } studied here (0.01–2.6). Mn 2+ exhibits much stronger log-linear growth rate inhibition at low Mn 2+ concentrations (fluid {Mn 2+ }/{Ca 2+ } = 0.001–0.02). Mn 2+ is readily incorporated into the calcite lattice to form a calcite-rhodochrosite solid solution, with large partition coefficients (K Mn 4.6–15.6) inversely correlated to growth rate. For both Mn 2+ and Mg 2+ , calcium isotope fractionation is found to be invariant with {Me 2+ }/{Ca 2+ } despite more than an order of magnitude decline in growth rate. This invariant Δ 44/40 Ca suggests that the presence of Mn 2 + or Mg 2+ does not significantly change the relative rates of Ca 2+ attachment and detachment at kink sites during growth, indicative of a dominantly kink blocking inhibition mechanism. Because the partitioning behavior dictates that Mn 2+ must attach to the surface significantly faster than Ca 2+ , attachment of Mn 2+ is likely to be as a non-monomer species such as an ion pair or possibly a larger polynuclear cluster. We propose that calcite growth rate inhibition by Mn is determined by the kinetics of carbonate attachment at Mn-occupied kink sites, potentially due to slow re-orientation kinetics of carbonate ions that have formed an inner-sphere complex with Mn 2+ at the surface but must reorient to incorporate into the lattice. We demonstrate that patterns in Mg 2+ partitioning and inhibition behavior are broadly consistent with growth inhibition driven by slow Mg 2+ -aquo complex dehydration relative to Ca 2+ but argue that this mechanism likely represents one endmember scenario, seen in Mg-calcite growth at low supersaturations and net precipitation rates. During growth at faster net precipitation rates, some portion of Mg 2+ is likely incorporated as a partially hydrated or otherwise complexed species, but calcite growth remains significantly inhibited by the kinetics of CO 3 2- attachment at Mg 2+ kink sites. These findings suggest a hybrid classical/nonclassical growth mechanism whereby Ca 2+ incorporates largely as a free ion at kink sites while Mn 2+ and some portion of Mg 2+ are incorporated via non-monomer attachment. This pattern may be generalizable; trace constituent cations with aquo-complex desolvation rates significantly slower than the mineral growth rate preferentially incorporate as a non-monomer species during otherwise classical crystal growth.

58 GEOSCIENCES↗
DOE OSTI2022

Analysis of Intermediates and Products from the Dehydrogenation of Mg(BH 4 ) 2

The thermodynamic properties of key compounds, Mg(B 3 H 8 ) 2 , MgB 2 H 6 , MgB 10 H 10 , Mg(B 11 H 14 ) 2 , Mg 3 (B 3 H 6 ) 2 , and MgB 12 H 12 , proposed to be formed in the release of hydrogen from magnesium borohydride Mg(BH 4 ) 2 and uptake of hydrogen by MgB 2 , have been investigated using solid–state density functional theory (DFT) calculations. Further, more accurate treatment of cell–size effects to the entropies were also investigated, in order to improve the accuracy of the thermodynamic properties of complex borohydrides. We find that the zero–point energy corrections can lower the electronic energies of reaction by 20–30 kJ/(mol H 2 ) for these intermediates, while adding the thermal and entropy contributions results in the total decrease up to ~50 kJ/(mol H 2 ). Although our treatment lowers the calculated formation energy of Mg(B 3 H 8 ) 2 , it is still too high to explain the experimental observation of B 3 H 8 – . We discuss possible reasons for this disparity and propose that the formation of B 3 H 8 – and H – in a disordered amorphous phase has a large energy difference compared to the phase–separated Mg(B 3 H 8 ) 2 and MgH 2 considered in calculations. Comparison of the experimental and NMR chemical shifts calculated within a DFT approach for known species Mg(BH 4 ) 2 , Mg(B 3 H 8 ) 2 , Mg(B 11 H 14 ) 2 , MgB 10 H 10 and MgB 12 H 12 provides validation for predicting the chemical shifts of the other compounds which are yet to be confirmed experimentally. These include MgB 2 H 6 and the proposed tri–anion species Mg 3 (B 3 H 6 ) 2 that both have favorable thermodynamics for reversible hydrogen storage in Mg(BH 4 ) 2 without the formation of MgH 2 as a co–product which could phase–separate and inhibit rehydrogenation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Solute effects upon dislocation motion and recovery in Mg alloys (Final Report)

The objective the research was to develop a firmer understanding of the interactions between substitutional solute atoms and dislocations within Mg alloys. These interactions govern the absolute and relative mobilities of various types of dislocations in Mg (e.g., basal < a>, non-basal < a>, and pyramidal < c+a>). Furthermore, they have an impact on dislocation recovery processes (e.g., cross-glide, climb, rearrangement, and annihilation). Ultimately, solute-dislocation interactions strongly impact a) strain hardening, b) strain rate sensitivity, c) plastic anisotropy of textured polycrystals, d) texture evolution, e) dislocation substructures evolution, and even f) recrystallization behavior. It is broadly known that Mg alloys exhibit poor low temperature formability. Since formability is largely governed by properties (a) – (c) in this list, it is critical to develop a better understanding of solute-dislocation interactions, if one hopes to improve the situation. While the theory of static solute strengthening is well developed, especially for alloys with face centered cubic (FCC) crystal structures, there are outstanding questions related to applications to hexagonal close packed (HCP) crystal structures and dynamic strain aging (DSA) in materials of various structures. DSA has far-reaching implications for metal formability and, in the case of Mg alloys, appears to correlate with the so-called rare-earth (RE) texture which has been shown to benefit formability. The Portevin-Le Chatelier (PLC) effect, and associated negative strain rate sensitivity, occur at higher temperatures (>100℃) in Mg alloys as compared with similar Al alloys, even though they have similar melting points and solute diffusivities. Our preliminary research has shown that modern, physics-based models of DSA can be tuned to describe the behavior of Mg alloys if a rather higher activation enthalpy is assumed for cross-core diffusivity. While this partially explains the delay in DSA to higher temperatures, it is also hypothesized that this delay is due in part to the intrinsically more thermally activated (rate sensitive) nature of non-basal < a> dislocation motion which is required for macroscopic flow of Mg alloys, whereas octahedral slip in many FCC metals like aluminum is essentially athermal at room temperature. It was originally proposed to employ a combination of in-situ diffraction-based experimental characterization to validate existing theory. It was envisioned to perform in-situ transmission electron microscopy (TEM) to assess individual dislocation behavior and in-situ high-energy X-ray diffraction (HEXRD) techniques which were showing great promise for elucidating collective dislocation behavior, 2 including recovery, especially if the contributions to various forms of diffraction peak broadening (𝜂𝜂,𝜔𝜔,and 2𝜃𝜃) can be effectively integrated. Finally, it was envisioned to perform discrete dislocation dynamics (DDD) modeling approaches to aide in the interpretation of both TEM and HEXRD experiments. In the end, mechanical tests were performed on more complex Mg alloys which exhibited evidence of dynamic strain aging, and this led to the establishment of another project. Mechanical test data obtained at McMaster University served as the basis of an assessment of the applicability of Bazinski’s “stress equivalence” theory of solute strengthening to polycrystalline alloys of Mg. Although we did not succeed in applying the approach to Mg alloys, we did develop expertise with the HEXRD approach using a BCC, β-Ti alloy and demonstrated numerous new capabilities that may be applied to any polycrystalline material in collaboration with researchers at CHESS and around the world: (1) assessment of details of the elastoplastic transition (yielding) using a combination of HEXRD and full-field polycrystal plasticity modeling, (2) the first-ever experimental observation of strong stress rotation within the individual grains of a polycrystalline material, and (3) a comprehensive analysis of the grain-level dislocation density evolution based upon diffraction peak broadening along 𝜂𝜂,𝜔𝜔,and 2𝜃𝜃 directions. This final aspect allowed us to confirm that dislocations were gliding on multiple plane types and not restricted to {110} type planes, and it also provided clues as to why some grains were unloading during straining, with surprising implications for our understanding of the effects of geometrically necessary dislocations (GNDs). Finally, graduate student, Mohammed Shabana, developed a MATLAB code which confirmed the conclusions of Prof. Catalin Picu (Rensallear Polytechnic Institute, RPI) regarding the effect of solute-trapped, forest dislocations on the breaking stress of Lomer lock junctions in FCC metal alloys. He applied the same anisotropic line-tension model to a variety of dislocation junction configurations and found an inconsistency in the widely cited results of Dupuy and Fivel regarding the Hirth Lock, and he outlined an approach to extend these finding to HCP Mg alloys that we are still pursuing with discretionary fundings at UVA.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(BO4)4 by Materials Project

Mg(B2O7)2O2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four hydrogen peroxide molecules and one Mg(B2O7)2 framework. In the Mg(B2O7)2 framework, Mg is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Mg–O bond distances ranging from 1.92–2.36 Å. There are four inequivalent B sites. In the first B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.34–1.46 Å. In the second B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.30–1.47 Å. In the third B site, B is bonded in a trigonal planar geometry to three O atoms. There is two shorter (1.36 Å) and one longer (1.41 Å) B–O bond length. In the fourth B site, B is bonded in a trigonal planar geometry to three O atoms. There are a spread of B–O bond distances ranging from 1.29–1.47 Å. There are fifteen inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to two O atoms. There is one shorter (1.31 Å) and one longer (1.48 Å) O–O bond length. In the second O site, O is bonded in a bent 150 degrees geometry to one Mg and one B atom. In the third O site, O is bonded in a bent 120 degrees geometry to two B atoms. In the fourth O site, O is bonded in a 2-coordinate geometry to one Mg, one B, and one O atom. The O–O bond length is 1.77 Å. In the fifth O site, O is bonded in a distorted bent 120 degrees geometry to two B atoms. In the sixth O site, O is bonded in a distorted single-bond geometry to one B and one O atom. In the seventh O site, O is bonded in a distorted single-bond geometry to one B and one O atom. The O–O bond length is 1.34 Å. In the eighth O site, O is bonded in a bent 120 degrees geometry to two O atoms. The O–O bond length is 1.74 Å. In the ninth O site, O is bonded in a linear geometry to two equivalent O atoms. In the tenth O site, O is bonded in a linear geometry to two equivalent O atoms. In the eleventh O site, O is bonded in a linear geometry to one Mg and one B atom. In the twelfth O site, O is bonded in a distorted single-bond geometry to one B and one O atom. The O–O bond length is 1.33 Å. In the thirteenth O site, O is bonded in a distorted trigonal planar geometry to one Mg and two B atoms. In the fourteenth O site, O is bonded in a single-bond geometry to one O atom. In the fifteenth O site, O is bonded in a bent 120 degrees geometry to one Mg and one O atom.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Synthesis of Mg–K-biochar bimetallic catalyst and its evaluation of glucose isomerization

Highly efficient isomerization of glucose to fructose is essential for valorizing cellulose fraction of biomass to value-added chemicals. This work provided an innovative method for preparing Mg-biochar and Mg–K-biochar catalysts by impregnating either MgCl 2 alone or in combination with different K compounds (Ding et al. in Bioresour Technol 341:125835, 2021, https://doi.org/10.1016/j.biortech.2021.125835 and KHCO 3 ) on cellulose-derived biochar, followed by hydrothermal carbonization and pyrolysis. Single active substance MgO existing in the 10 Mg–C could give better catalytic effect on glucose isomerization than the synergy of MgO and KCl crystalline material present in 10 Mg–KCl–C. But the catalytic effect of 10 Mg–C was decreased when the basic site of MgO was overloaded. Compared to other carbon-based metal catalysts, 10 Mg–KHCO3–C with 10 wt% MgCl 2 loading had excellent catalytic performance, which gave a higher fructose yield (36.7%) and selectivity (74.54%), and catalyzed excellent glucose conversion (53.99%) at 100 °C in 30 min. Scanning electron microscope–energy dispersive spectrometer and X-Ray diffraction revealed that the distribution of Mg 2+ and K+ in 10 Mg–KHCO 3 –C was uniform and the catalytic active substances (MgO, KCl and K2CO 3 ) were more than 10 Mg–C (only MgO). The synergy effects of MgO and K 2 CO 3 active sites enhanced the pH of reaction system and induced H 2 O ionization to form considerable OH– ions, thus easily realizing a deprotonation of glucose and effectively catalyzing the isomerization of glucose. In this study, we developed a highly efficient Mg–K-biochar bimetallic catalyst for glucose isomerization and provided an efficient method for cellulose valorization.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Ab initio thermodynamics of Ni and Co incorporation in Mg hydroxide, carbonate, and hydroxycarbonate minerals

Ni and Co are critical elements needed for modern technologies, and a better understanding of the ability of Mg-based minerals to incorporate these elements would benefit strategy development for Ni and Co recovery from mafic and ultramafic deposits. Here, in this work, we performed density functional theory (DFT) calculations of Ni and Co incorporation in six potential products of the carbonation of mafic and ultramafic silicates: brucite (Mg(OH) 2 ), magnesite (MgCO 3 ), nesquehonite (MgCO 3 ⸱3H 2 O), lansfordite (MgCO 3 ⸱5H 2 O), artinite (Mg 2 CO 3 (OH) 2 ⸱3H 2 O), and hydromagnesite (Mg 5 (CO 3 ) 4 (OH) 2 ⸱4H 2 O). The DFT results were used in an ab initio thermodynamics framework to explore the pH 2 O–pCO 2 conditions at which the Mg-based minerals were predicted to be thermodynamically stable and to quantify the Gibbs free energy of Ni and Co substitution at Mg sites. Among the six Mg-based minerals, brucite and magnesite were predicted to have the lowest Ni and Co substitution free energy. An analysis of the effect of temperature indicated that, at low temperature (<100 K), brucite more readily accommodated Ni and Co, while, at higher temperature (>335 K), magnesite more favorably incorporated Ni and Co. Between 100 K and 335 K, Ni was predicted to preferentially substitute for Mg in brucite and Co for Mg in magnesite, thus leading to a driving force for separating Ni and Co in conditions where brucite and magnesite both form. Insights gained in this work could therefore help select experimental conditions that either promote or inhibit incorporation of these critical elements into Mg-based mineral phases.

Critical elements↗
DOE OSTI2022

Proton branching ratios of 23 Mg levels

Background: The anomalous 22 Ne abundance measured in certain presolar graphite grains is thought to arise from the decay of 22 Na that was synthesized at high temperatures in core-collapse supernovae. To better interpret this abundance anomaly, the primary destruction mechanism of 22 Na, the 22 Na(p,γ) 23 Mg reaction, must be better understood. Purpose: Determine proton branching ratios of several 23 Mg excited states that play a role in the high-temperature 22 Na(p,γ) 23 Mg reaction rate. Methods: Particle decays of 23 Mg excited states populated with the previously reported 24 Mg(p,d) 23 Mg transfer reaction measurement [Kwag et al., Eur. Phys. J. A 56, 108 (2020)] were analyzed to extract proton branching ratios. The reaction was studied using a 31-MeV proton beam from the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory and 24 Mg solid targets. Results: Proton branching ratios of several 23 Mg excited states in the energy range of Ex = 8.044 - 9.642 MeV were experimentally determined for the first time for the p0 and p1'(p1+p2+p3) decay channels. Conclusions: These new branching ratios for 23 Mg levels can provide an experimental foundation for an improved high-temperature rate of the 22 Na(p,γ) 23 Mg reaction needed to understand production of anomalously high 22 Ne abundance in core-collapse supernovae.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Laser Plasma Interaction in the MG Magnetic Field (Final Report)

Strong magnetic fields change properties of plasma. Employment of the magnetic fields can improve conditions for inertial confinement fusion. Compression and heating of the magnetized plasma is a base of the MagLIF pulsed power approach to the controlled fusion. Study of expansion and heating of plasma in the external magnetic fields, development of plasma instabilities, parametric and other effects are important for basic physics and applications. The main goal of the research for the grant was experimental investigation of laser produced plasma in the well characterized and controlled MG magnetic fields. We developed a platform for investigation of high intensity laser-plasma interaction (LPI) in the MG fields using a university-scale pulsed power machine. A Zebra machine at UNR generated transverse magnetic fields of 3 MG on the surface of the rod load and longitudinal fields of 1.4 MG in the coil loads. The magnetic fields were characterized with two-color Faraday rotation diagnostics. The pulsed power machine provided almost static magnetic fields for LPI compared to the much faster laser driven magnetic fields. We found that eddy currents in the rising magnetic field generate plasma on the metal targets. Eddy currents did not impact Si and CH dielectric targets. A Leopard laser with intensity in the focus up to 10 19 W/cm 2 produced plasma in the MG magnetic fields. The modified reflected Faraday diagnostics was used to study laser driven B-field at the MTW laser at Laboratory for Laser Energetics, UR. We demonstrated a slow dependence of the magnetic field in the coil on the applied laser intensity. The magnetic field increased by a factor of 2 if laser intensity increased by a factor of 30. This scaling is important for comparison of experiments at different laser facilities. Expansion of the plasma in the 2-3 MG external B-field was studied. Laser-produced plasma in the azimuthal magnetic field took the unique form of a thin disc expanding radially with a velocity of 250 km/s and confined in the vertical direction. A HYDRA MHD program at the University of Rochester was applied for simulations of LPI in the magnetic field B >3 MG. Simulations for the plasma disc parameters and the expansion dynamics were in a good agreement with experiments. Generation of narrow dense plasma jets in the longitudinal magnetic field of 0.6-0.8 MG was studied. Narrow plasma jets reached a length of 3-4 mm with the electron plasma density of (0.2-1.2)x10 20 cm -3 . A jet tip propagated with the velocity of 160-200 km/s. MHD simulations showed a good agreement of the dynamics of the formation of plasma jets with experiments. These jets are relevant to astrophysical jets. Simulations of K-shell spectra of Si plasma was performed for LPI in the B-field. The laser prepulse generated plasma near the laser target. A PrismSPECT model with a MeV electron beam produced by the laser was used. The spectral modelling showed the increased plasma density by a factor by 2-3 in the magnetic field. This was in agreement with the observed dynamics of the plasma plume confined by the axial magnetic field. The two-plasmon decay was studied in the 2.5-3 MG transversal magnetic fields. Strong 2-3.5 nm spectral widening and a 2-4 nm shifts of “red” and “blue” 3/2ω 0 spectral components were observed. The large shift and widening exceed the expected temperature and magnetic shift. PIC simulations are performing to clarify physics of this effect. The experimental research program for the grant is completed. New plasma effects in the MG fields were studied at the university-scale pulsed power generator. Two graduate and two undergraduate UNR and UR students carried experiments at the Zebra generator, supported and developed plasma diagnostics, provided data processing, and performed MHD simulations of LPI in the strong magnetic field. Research results are published in 9 referred papers and presented in 12 conferences. Program manager: Kramer U. Akli; Collaborators: R. C. Mancini and H. Sawada, University of Nevada, Reno (UNR); R. Betti and A. V. Maximov, University of Rochester (UR).

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Materials Data on Mg(AgO2)2 by Materials Project

Mg(AgO2)2 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AgO6 octahedra. The corner-sharing octahedra tilt angles range from 49–63°. There are two shorter (2.03 Å) and two longer (2.08 Å) Mg–O bond lengths. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AgO4 tetrahedra, and edges with six AgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.12–2.15 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AgO6 octahedra. The corner-sharing octahedra tilt angles range from 51–62°. There are a spread of Mg–O bond distances ranging from 2.06–2.09 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four AgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.10–2.15 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six AgO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent AgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.14 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six AgO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.16 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.16 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six AgO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.10–2.15 Å. There are twelve inequivalent Ag3+ sites. In the first Ag3+ site, Ag3+ is bonded to six O2- atoms to form AgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AgO6 octahedra. There are a spread of Ag–O bond distances ranging from 2.10–2.25 Å. In the second Ag3+ site, Ag3+ is bonded to six O2- atoms to form AgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AgO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AgO6 octahedra. There are a spread of Ag–O bond distances ranging from 2.10–2.21 Å. In the third Ag3+ site, Ag3+ is bonded to four O2- atoms to form AgO4 tetrahedra that share corners with six MgO6 octahedra and corners with six AgO6 octahedra. The corner-sharing octahedra tilt angles range from 57–66°. There are a spread of Ag–O bond distances ranging from 2.18–2.24 Å. In the fourth Ag3+ site, Ag3+ is bonded to six O2- atoms to form AgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four AgO4 tetrahedra, edges with three MgO6 octahedra, and edges with three AgO6 octahedra. There are a spread of Ag–O bond distances ranging from 2.06–2.26 Å. In the fifth Ag3+ site, Ag3+ is bonded to four O2- atoms to form AgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AgO6 octahedra. The corner-sharing octahedra tilt angles range from 57–64°. There are one shorter (2.10 Å) and three longer (2.20 Å) Ag–O bond lengths. In the sixth Ag3+ site, Ag3+ is bonded to four O2- atoms to form AgO4 tetrahedra that share corners with six MgO6 octahedra and corners with six AgO6 octahedra. The corner-sharing octahedra tilt angles range from 55–65°. There are a spread of Ag–O bond distances ranging from 2.17–2.20 Å. In the seventh Ag3+ site, Ag3+ is bonded to six O2- atoms to form AgO6 octahedra that share corners with six AgO4 tetrahedra, edges with two equivalent AgO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Ag–O bond distances ranging from 2.07–2.15 Å. In the eighth Ag3+ site, Ag3+ is bonded to four O2- atoms to form AgO4 tetrahedra that share corners with six MgO6 octahedra and corners with six AgO6 octahedra. The corner-sharing octahedra tilt angles range from 56–65°. There are a spread of Ag–O bond distances ranging from 2.13–2.18 Å. In the ninth Ag3+ site, Ag3+ is bonded to six O2- atoms to form AgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AgO4 tetrahedra, edges with three MgO6 octahedra, and edges with three AgO6 octahedra. There are a spread of Ag–O bond distances ranging from 2.05–2.20 Å. In the tenth Ag3+ site, Ag3+ is bonded to four O2- atoms to form AgO4 tetrahedra that share corners with six MgO6 octahedra and corners with six AgO6 octahedra. The corner-sharing octahedra tilt angles range from 55–65°. There are two shorter (2.18 Å) and two longer (2.19 Å) Ag–O bond lengths. In the eleventh Ag3+ site, Ag3+ is bonded to six O2- atoms to form AgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AgO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AgO6 octahedra. There are a spread of Ag–O bond distances ranging from 2.12–2.25 Å. In the twelfth Ag3+ site, Ag3+ is bonded to four O2- atoms to form AgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AgO6 octahedra. The corner-sharing octahedra tilt angles range from 58–63°. There are one shorter (2.13 Å) and three longer (2.21 Å) Ag–O bond lengths. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ag3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Ag3+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Ag3+ atoms. In the fourth O2- site, O2- is bonded to four Ag3+ atoms to form a mixture of distorted edge and corner-sharing OAg4 trigonal pyramids. In the fifth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Ag3+ atoms. In the sixth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 tetrahedra that share a cornercorner with one OMgAg3 tetrahedra, corners with two OMgAg3 trigonal pyramids, edges with two OMgAg3 tetrahedra, and an edgeedge with one OAg4 trigonal pyramid. In the seventh O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 tetrahedra that share corners with six OMg2Ag2 tetrahedra and corners with six OMgAg3 trigonal pyramids. In the eighth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 tetrahedra that share corners with two equivalent OMgAg3 tetrahedra, a cornercorner with one OAg4 trigonal pyramid, edges with two equivalent OMgAg3 tetrahedra, and an edgeedge with one OAg4 trigonal pyramid. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Ag3+ atoms. In the tenth O2- site, O2- is bonded to two Mg2+ and two Ag3+ atoms to form distorted OMg2Ag2 tetrahedra that share corners with seven OMg2Ag2 tetrahedra, corners with five OMgAg3 trigonal pyramids, an edgeedge with one OMg2Ag2 tetrahedra, and edges with two OMgAg3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with six OMgAg3 tetrahedra, corners with two OMgAg3 trigonal pyramids, edges with two equivalent OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the twelfth O2- site, O2- is bonded to two Mg2+ and two Ag3+ atoms to form distorted OMg2Ag2 tetrahedra that share corners with five OMgAg3 tetrahedra, corners with three OMgAg3 trigonal pyramids, an edgeedge with one OMg2Ag2 tetrahedra, and edges with two OMgAg3 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with six OMg2Ag2 tetrahedra, corners with six OMgAg3 trigonal pyramids, edges with two equivalent OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with five OMgAg3 tetrahedra, a cornercorner with one OAg4 trigonal pyramid, edges with two equivalent OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the fifteenth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with seven OMg2Ag2 tetrahedra, corners with five OMgAg3 trigonal pyramids, edges with two equivalent OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with six OMg2Ag2 tetrahedra, corners with six OMgAg3 trigonal pyramids, edges with two equivalent OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the seventeenth O2- site, O2- is bonded to two Mg2+ and two Ag3+ atoms to form distorted OMg2Ag2 tetrahedra that share corners with six OMg2Ag2 tetrahedra, corners with six OMgAg3 trigonal pyramids, an edgeedge with one OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the eighteenth O2- site, O2- is bonded to two Mg2+ and two Ag3+ atoms to form distorted OMg2Ag2 tetrahedra that share corners with six OMg2Ag2 tetrahedra, corners with six OMgAg3 trigonal pyramids, an edgeedge with one OMg2Ag2 tetrahedra, and edges with two OMgAg3 trigonal pyramids. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Ag3+ atoms. In the twentieth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with six OMg2Ag2 tetrahedra, corners with six OMgAg3 trigonal pyramids, edges with two equivalent OMg2Ag2 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the twenty-first O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with six OMg2Ag2 tetrahedra, corners with six OMgAg3 trigonal pyramids, and edges with two equivalent OMg2Ag2 tetrahedra. In the twenty-second O2- site, O2- is bonded to four Ag3+ atoms to form distorted OAg4 trigonal pyramids that share corners with five OMg2Ag2 tetrahedra, corners with two equivalent OMgAg3 trigonal pyramids, edges with two equivalent OMgAg3 tetrahedra, and an edgeedge with one OMgAg3 trigonal pyramid. In the twenty-third O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 tetrahedra that share corners with five OMg2Ag2 tetrahedra, corners with two OMgAg3 trigonal pyramids, an edgeedge with one OMgAg3 tetrahedra, and edges with two OAg4 trigonal pyramids. In the twenty-fourth O2- site, O2- is bonded to one Mg2+ and three Ag3+ atoms to form distorted OMgAg3 trigonal pyramids that share corners with six OMg2Ag2 tetrahedra, corners with three OMgAg3 trigonal pyramids, edges with two equivalent OMgAg3 tetrahedra, and an edgeedge with one OAg4 trigonal pyramid.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg(SnO2)2 by Materials Project

Mg(SnO2)2 is Ilmenite-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 54–59°. There are a spread of Mg–O bond distances ranging from 2.03–2.74 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra and edges with five SnO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.22 Å. In the third Mg2+ site, Mg2+ is bonded in a distorted trigonal non-coplanar geometry to four O2- atoms. There are a spread of Mg–O bond distances ranging from 1.99–2.80 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three SnO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five SnO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.30 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six SnO4 tetrahedra, edges with two MgO6 octahedra, and edges with four equivalent SnO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.24 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share corners with six SnO4 tetrahedra, edges with two MgO6 octahedra, and edges with four SnO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.26–2.32 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with three SnO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with four equivalent SnO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.11–2.35 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share corners with six SnO4 tetrahedra, edges with two MgO6 octahedra, and edges with four SnO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.22–2.32 Å. There are twelve inequivalent Sn3+ sites. In the first Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with two equivalent MgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with three SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.06–2.20 Å. In the second Sn3+ site, Sn3+ is bonded to six O2- atoms to form distorted SnO6 octahedra that share edges with two MgO6 octahedra and edges with four SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.32–2.70 Å. In the third Sn3+ site, Sn3+ is bonded to four O2- atoms to form SnO4 tetrahedra that share corners with six MgO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 56–69°. There are a spread of Sn–O bond distances ranging from 2.19–2.71 Å. In the fourth Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with three SnO4 tetrahedra, edges with three MgO6 octahedra, and edges with three SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.06–2.21 Å. In the fifth Sn3+ site, Sn3+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Sn–O bond distances ranging from 2.11–2.79 Å. In the sixth Sn3+ site, Sn3+ is bonded to four O2- atoms to form SnO4 tetrahedra that share corners with six MgO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 58–66°. There are a spread of Sn–O bond distances ranging from 2.21–2.67 Å. In the seventh Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six SnO4 tetrahedra, edges with two equivalent SnO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.08–2.16 Å. In the eighth Sn3+ site, Sn3+ is bonded to four O2- atoms to form SnO4 tetrahedra that share corners with six MgO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 55–70°. There are a spread of Sn–O bond distances ranging from 2.20–2.59 Å. In the ninth Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with three SnO4 tetrahedra, edges with two equivalent SnO6 octahedra, and edges with three MgO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.08–2.16 Å. In the tenth Sn3+ site, Sn3+ is bonded to four O2- atoms to form SnO4 tetrahedra that share corners with six MgO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 56–71°. There are a spread of Sn–O bond distances ranging from 2.20–2.55 Å. In the eleventh Sn3+ site, Sn3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Sn–O bond distances ranging from 2.32–2.73 Å. In the twelfth Sn3+ site, Sn3+ is bonded in a 3-coordinate geometry to three O2- atoms. There are two shorter (2.12 Å) and one longer (2.19 Å) Sn–O bond lengths. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Mg2+ and two Sn3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Sn2 trigonal pyramids. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+ and two equivalent Sn3+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three Sn3+ atoms. In the fourth O2- site, O2- is bonded to four Sn3+ atoms to form distorted corner-sharing OSn4 trigonal pyramids. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+ and two Sn3+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three Sn3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form distorted corner-sharing OMgSn3 tetrahedra. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two equivalent Sn3+ atoms. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Sn3+ atoms. In the tenth O2- site, O2- is bonded to two Mg2+ and two Sn3+ atoms to form a mixture of corner and edge-sharing OMg2Sn2 tetrahedra. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form OMgSn3 tetrahedra that share corners with eight OMgSn3 tetrahedra and edges with two equivalent OMg2Sn2 tetrahedra. In the twelfth O2- site, O2- is bonded to two Mg2+ and two Sn3+ atoms to form a mixture of corner and edge-sharing OMg2Sn2 tetrahedra. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form a mixture of distorted corner and edge-sharing OMgSn3 tetrahedra. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and three Sn3+ atoms. In the fifteenth O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form OMgSn3 tetrahedra that share corners with twelve OMgSn3 tetrahedra and edges with three OMg2Sn2 tetrahedra. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form a mixture of corner and edge-sharing OMgSn3 tetrahedra. In the seventeenth O2- site, O2- is bonded to two Mg2+ and two Sn3+ atoms to form a mixture of corner and edge-sharing OMg2Sn2 tetrahedra. In the eighteenth O2- site, O2- is bonded to two Mg2+ and two Sn3+ atoms to form a mixture of corner and edge-sharing OMg2Sn2 tetrahedra. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Sn3+ atoms. In the twentieth O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form a mixture of distorted corner and edge-sharing OMgSn3 tetrahedra. In the twenty-first O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form OMgSn3 tetrahedra that share corners with eight OMgSn3 tetrahedra and edges with two equivalent OMg2Sn2 tetrahedra. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to four Sn3+ atoms. In the twenty-third O2- site, O2- is bonded in a 4-coordinate geometry to one Mg2+ and three Sn3+ atoms. In the twenty-fourth O2- site, O2- is bonded to one Mg2+ and three Sn3+ atoms to form distorted corner-sharing OMgSn3 tetrahedra.

36 MATERIALS SCIENCE↗