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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Pr3Cr10N11 by Materials Project

Pr3Cr10N11 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pr3+ is bonded in a 9-coordinate geometry to nine N3- atoms. There are a spread of Pr–N bond distances ranging from 2.55–2.77 Å. There are two inequivalent Cr+2.40+ sites. In the first Cr+2.40+ site, Cr+2.40+ is bonded to four N3- atoms to form a mixture of corner and edge-sharing CrN4 trigonal pyramids. There is two shorter (1.92 Å) and two longer (1.96 Å) Cr–N bond length. In the second Cr+2.40+ site, Cr+2.40+ is bonded to four N3- atoms to form a mixture of distorted corner and edge-sharing CrN4 tetrahedra. There is three shorter (1.86 Å) and one longer (2.13 Å) Cr–N bond length. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted square co-planar geometry to two equivalent Pr3+ and four Cr+2.40+ atoms. In the second N3- site, N3- is bonded to three equivalent Pr3+ and three equivalent Cr+2.40+ atoms to form distorted NPr3Cr3 octahedra that share corners with six equivalent NPr3Cr3 octahedra, edges with three equivalent NPr3Cr3 octahedra, and a faceface with one NPr6 octahedra. The corner-sharing octahedra tilt angles range from 28–35°. In the third N3- site, N3- is bonded to six equivalent Pr3+ atoms to form face-sharing NPr6 octahedra. In the fourth N3- site, N3- is bonded in a body-centered cubic geometry to eight equivalent Cr+2.40+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ce3Cr10N11 by Materials Project

Ce3Cr10N11 crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ce3+ is bonded in a 9-coordinate geometry to nine N3- atoms. There are a spread of Ce–N bond distances ranging from 2.47–2.77 Å. There are two inequivalent Cr+2.40+ sites. In the first Cr+2.40+ site, Cr+2.40+ is bonded in a rectangular see-saw-like geometry to four N3- atoms. There are two shorter (1.97 Å) and two longer (2.04 Å) Cr–N bond lengths. In the second Cr+2.40+ site, Cr+2.40+ is bonded to four N3- atoms to form a mixture of distorted corner and edge-sharing CrN4 tetrahedra. There are three shorter (1.83 Å) and one longer (2.17 Å) Cr–N bond lengths. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ce3+ and four Cr+2.40+ atoms. In the second N3- site, N3- is bonded to three equivalent Ce3+ and three equivalent Cr+2.40+ atoms to form distorted NCe3Cr3 octahedra that share corners with six equivalent NCe3Cr3 octahedra, edges with three equivalent NCe3Cr3 octahedra, and a faceface with one NCe6 octahedra. The corner-sharing octahedra tilt angles range from 20–32°. In the third N3- site, N3- is bonded to six equivalent Ce3+ atoms to form face-sharing NCe6 octahedra. In the fourth N3- site, N3- is bonded in a body-centered cubic geometry to eight equivalent Cr+2.40+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2Cr2Fe15 by Materials Project

Y2Fe15Cr2 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded in a 8-coordinate geometry to two equivalent Cr and eighteen Fe atoms. Both Y–Cr bond lengths are 3.06 Å. There are a spread of Y–Fe bond distances ranging from 2.99–3.19 Å. In the second Y site, Y is bonded in a 6-coordinate geometry to eighteen Fe atoms. There are a spread of Y–Fe bond distances ranging from 2.95–3.25 Å. Cr is bonded in a 1-coordinate geometry to one Y, one Cr, and twelve Fe atoms. The Cr–Cr bond length is 2.18 Å. There are a spread of Cr–Fe bond distances ranging from 2.61–2.71 Å. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to two equivalent Y, two equivalent Cr, and eight Fe atoms to form FeY2Cr2Fe8 cuboctahedra that share corners with twenty-two FeY3CrFe8 cuboctahedra, edges with ten FeY3CrFe8 cuboctahedra, and faces with eighteen FeY2Cr2Fe8 cuboctahedra. There are four shorter (2.42 Å) and four longer (2.44 Å) Fe–Fe bond lengths. In the second Fe site, Fe is bonded to three Y, one Cr, and eight Fe atoms to form distorted FeY3CrFe8 cuboctahedra that share corners with twenty-three FeY3CrFe8 cuboctahedra, edges with ten FeY3CrFe8 cuboctahedra, and faces with twenty FeY2Cr2Fe8 cuboctahedra. There are a spread of Fe–Fe bond distances ranging from 2.43–2.62 Å. In the third Fe site, Fe is bonded to two Y, two equivalent Cr, and eight Fe atoms to form a mixture of distorted face, edge, and corner-sharing FeY2Cr2Fe8 cuboctahedra. There are one shorter (2.43 Å) and one longer (2.52 Å) Fe–Fe bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Be4CrMo by Materials Project

Be4MoCr is Hexagonal Laves-derived structured and crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are three inequivalent Be sites. In the first Be site, Be is bonded to six equivalent Be and six equivalent Cr atoms to form BeBe6Cr6 cuboctahedra that share corners with twelve equivalent BeBe6Cr3Mo3 cuboctahedra, edges with six equivalent BeBe6Cr6 cuboctahedra, and faces with twenty BeBe6Mo6 cuboctahedra. All Be–Be bond lengths are 2.14 Å. All Be–Cr bond lengths are 2.54 Å. In the second Be site, Be is bonded to six equivalent Be and six equivalent Mo atoms to form BeBe6Mo6 cuboctahedra that share corners with twelve equivalent BeBe6Cr3Mo3 cuboctahedra, edges with six equivalent BeBe6Mo6 cuboctahedra, and faces with twenty BeBe6Cr6 cuboctahedra. All Be–Be bond lengths are 2.23 Å. All Be–Mo bond lengths are 2.55 Å. In the third Be site, Be is bonded to six Be, three equivalent Mo, and three equivalent Cr atoms to form BeBe6Cr3Mo3 cuboctahedra that share corners with eighteen BeBe6Cr6 cuboctahedra, edges with six equivalent BeBe6Cr3Mo3 cuboctahedra, and faces with eighteen BeBe6Cr6 cuboctahedra. There are two shorter (2.13 Å) and two longer (2.22 Å) Be–Be bond lengths. There are two shorter (2.57 Å) and one longer (2.61 Å) Be–Mo bond lengths. There are one shorter (2.47 Å) and two longer (2.53 Å) Be–Cr bond lengths. Mo is bonded in a 3-coordinate geometry to twelve Be, three equivalent Mo, and one Cr atom. All Mo–Mo bond lengths are 2.68 Å. The Mo–Cr bond length is 2.66 Å. Cr is bonded in a 1-coordinate geometry to twelve Be, one Mo, and three equivalent Cr atoms. All Cr–Cr bond lengths are 2.65 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2TiCr3O8 by Materials Project

Li2TiCr3O8 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Li1+ is bonded to six O2- atoms to form LiO6 octahedra that share corners with six equivalent CrO6 octahedra, edges with two equivalent LiO6 octahedra, edges with two equivalent TiO6 octahedra, and edges with four CrO6 octahedra. The corner-sharing octahedra tilt angles range from 10–11°. There are a spread of Li–O bond distances ranging from 2.17–2.25 Å. Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share edges with four equivalent LiO6 octahedra and edges with six CrO6 octahedra. There is two shorter (1.97 Å) and four longer (1.98 Å) Ti–O bond length. There are two inequivalent Cr+3.33+ sites. In the first Cr+3.33+ site, Cr+3.33+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six equivalent LiO6 octahedra, edges with two equivalent LiO6 octahedra, edges with two equivalent TiO6 octahedra, and edges with four CrO6 octahedra. The corner-sharing octahedra tilt angles range from 10–11°. There are a spread of Cr–O bond distances ranging from 2.02–2.05 Å. In the second Cr+3.33+ site, Cr+3.33+ is bonded to six O2- atoms to form CrO6 octahedra that share edges with two equivalent TiO6 octahedra, edges with four equivalent LiO6 octahedra, and edges with four equivalent CrO6 octahedra. There is four shorter (1.94 Å) and two longer (1.98 Å) Cr–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Li1+, one Ti4+, and two Cr+3.33+ atoms. In the second O2- site, O2- is bonded to two equivalent Li1+ and three Cr+3.33+ atoms to form OLi2Cr3 square pyramids that share corners with five equivalent OLi2Cr3 square pyramids and edges with four equivalent OLi2TiCr2 square pyramids. In the third O2- site, O2- is bonded to two equivalent Li1+, one Ti4+, and two equivalent Cr+3.33+ atoms to form OLi2TiCr2 square pyramids that share corners with five equivalent OLi2TiCr2 square pyramids and edges with four equivalent OLi2Cr3 square pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Chromium isotope fractionation during reduction of Chromium(VI) by Iron(II/III)-bearing clay minerals

Chromium stable isotope ratios are used to trace the reduction of Cr(VI) to Cr(III) in both ancient and modern systems. However, quantitative interpretation of Cr isotopic signatures has been stymied by the large variability in isotopic fractionation factors for Cr(VI) reduction by different reductants. Here we determine Cr isotope fractionation factors during Cr(VI) reduction by Fe(II/III)-bearing clay minerals, which are abundant in subsurface environments. Several variables were tested: pH, total Fe content of the clay, and the fraction of reduced Fe within the clay (Fe(II)/Fe(total)). The latter controls the standard reduction potential of the clay. Our results demonstrate that neither pH nor total Fe content of the clay have major effects on isotopic fractionation. In contrast, as the effective standard reduction potential of the clay and thus the standard free energy of Cr(VI) reduction become more negative, Cr isotope fractionation factors decrease in magnitude from - 4.9 to -1.3‰ according to a linear free energy relationship. This linear free energy relationship can be predicted from Marcus electron transfer theory and allows first-order predictions of Cr isotope fractionation factors to be made from the standard reduction potential or Fe(II)/Fe(total) of a clay, potentially improving our ability to model Cr isotope signatures in geochemical systems. Chromium is the first isotope system to show such a linear free energy relationship over a diverse range of reductants, including both aqueous and solid-phase reductants, and may provide a model for determining other redox-driven kinetic isotope effects in environmentally important isotope systems.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

The Novel Hybrid Ab Initio Model of High-Performance Structural Alloys Design for Fossil Energy Power Plants

The current project developed a novel HT-CALPHAD/DFT approach, which can quickly design new high-performance structural alloys for the application of FE power plants. The PI will mainly take charge of high-throughput DFT simulations and computational thermodynamics of the selected multicomponent alloy systems for the FE power plant applications. At the end of the project, a novel hybrid model based on high throughput CALPHAD/DFT simulations and computational thermodynamics will be developed to provide guidance on how to identify multi-component new high-performance structural alloys with much less computational effort needed. It will address the extensive computation time needed for DFT on the new alloys design. In addition, it will also address the well-known headache of DFT, i.e. how to make the accurate prediction of the high-temperature equilibria. The novel hybrid model the PI proposed will not only be applied to the design of high-performance structural alloys in FE power plants but in many different applications, such as nuclear reactors. This hybrid modeling approach includes four sections: 1) HT-CALPHAD modeling of Al-Co-Cr-Ni-Fe system with FCC and BCC phase. In this section, 3561 non-equiatomic compositions were randomly generated in order to investigate the phase stability of single FCC and BCC phases. Meanwhile, we proposed a data screening procedure to screen out the good candidates within these compositions, considering the temperature range, average density, and melting temperature, etc. 2) Investigation of FCC-Cr lattice stability in Fe-Cr system. We systematically assessed the reliability of FCC-Cr lattice stability derived by DFT and CALPHAD approaches. Meanwhile, the Fe-Cr binary system was chosen as a case study to verify the Cr lattice stability obtained by both approaches. 3) High-throughput DFT modeling on elastic properties of Al-Co-Cr-Ni-Fe systems. We predicted and established the FCC quinary elastic constant database of the Al-Co-Cr-Fe-Ni systems at 0K by using special quasi-random structure (SQS) approach. The predictions will start with pure elements of Al-Co-Cr-Fe-Ni system and will be continued with binaries, ternaries, quaternaries, and finally the quinary compositions. 3) Modeling of temperature-dependent elastic properties in Al-Co-Cr-Ni-Fe systems. In this part, we predict the thermal expansion coefficient and elastic stiffness coefficient as a function of temperature by applying quasiharmonic approximation. With this approach, the elastic properties of HEAs at elevate temperature can be estimated.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Ab Initio Phase Diagram of Chromium to 2.5 TPa

Chromium possesses remarkable physical properties such as hardness and corrosion resistance. Chromium is also a very important geophysical material as it is assumed that lighter Cr isotopes were dissolved in the Earth’s molten core during the planet’s formation, which makes Cr one of the main constituents of the Earth’s core. Unfortunately, Cr has remained one of the least studied 3d transition metals. In a very recent combined experimental and theoretical study (Anzellini et al., Scientific Reports, 2022), the equation of state and melting curve of chromium were studied to 150 GPa, and it was determined that the ambient body-centered cubic (bcc) phase of crystalline Cr remains stable in the whole pressure range considered. However, the importance of the knowledge of the physical properties of Cr, specifically its phase diagram, necessitates further study of Cr to higher pressure. In this work, using a suite of ab initio quantum molecular dynamics (QMD) simulations based on the Z methodology which combines both direct Z method for the simulation of melting curves and inverse Z method for the calculation of solid–solid phase transition boundaries, we obtain the theoretical phase diagram of Cr to 2.5 TPa. We calculate the melting curves of the two solid phases that are present on its phase diagram, namely, the lower-pressure bcc and the higher-pressure hexagonal close-packed (hcp) ones, and obtain the equation for the bcc-hcp solid–solid phase transition boundary. We also obtain the thermal equations of state of both bcc-Cr and hcp-Cr, which are in excellent agreement with both experimental data and QMD simulations. We argue that 2180 K as the value of the ambient melting point of Cr which is offered by several public web resources (“Wikipedia,” “WebElements,” “It’s Elemental,” etc.) is most likely incorrect and should be replaced with 2135 K, found in most experimental studies as well as in the present theoretical work.

equation of state↗
NASA NTRS1996

Spectra of High-Ionization Seyfert 1 Galaxies: Implications for the Narrow-Line Region

We present line profiles and profile parameters for the Narrow-Line Regions (NLRs) of six Seyfert 1 galaxies with high-ionization lines: MCG 8-11-11, Mrk 79, Mrk 704, Mrk 841, NGC 4151, and NGC 5548. The sample was chosen primarily with the goal of obtaining high-quality [Fe VII] lambda6087 and, when possible, [Fe X] lambda6374 profiles to determine if these lines are more likely formed in a physically distinct 'coronal line region' or are formed throughout the NLR along with lines of lower critical density (n(sub cr)) and/or Ionization Potential (IP). We discuss correlations of velocity shift and width with n(sub cr) and IP. In some objects, lines of high IP and/or n(sub cr) are systematically broader than those of low IP/n(sub cr). Of particular interest, however, are objects that show no correlations of line width with either IP or n(sub cr). In these objects, lines of high and low IP/n(sub cr), are remarkably similar, which is difficult to reconcile with the classical picture of the NLR, in which lines of high and low IP/n(sub cr) are formed in physically distinct regions. We argue for similar spatial extents for the flux in lines with similar profiles. Here, as well as in a modeling-oriented companion paper, we develop further an idea suggested by Moore & Cohen that objects that do and do not show line width correlations with IP/n(sub cr) can both be explained in terms of a single NLR model with only a small difference in the cloud column density distinguishing the two types of object. Overall, our objects do not show correlations between the Full Width at Half-Maximum (FWHM) and IP and/or n(sub cr). The width must be defined by a parameter that is sensitive to extended profile wings in order for the correlations to result. We present models in which FWHM correlations with IP and/or n(sub cr) result only after simulating the lower spectral resolution used in previous observational studies. The models that simulate the higher spectral resolution of our observational study produce line width correlations only if the width is defined by a parameter that is more sensitive to extended profile wings than is the FWHM. Our sample of six objects is in effect augmented by incorporating the larger sample (16 objects) of Veilleux into some of our discussion. This paper focuses on new interpretations of NLR emission-line spectra and line profiles that stem directly from the observations. Paper 2 focuses on modeling and complements this paper by illustrating explicitly the effects that spatial variations in electron density, ionization parameter, and column density have on model profiles. By comparing model profiles with the observed profiles presented here, as well as with those presented by Veilleux, Paper 2 yields insight into how the electron density, ionization parameter, and column density likely vary throughout the NLR.

Moore, David↗
NASA NTRS2010

Thermal Expansion of Vacuum Plasma Sprayed Coatings

Metallic Cu-8%Cr, Cu-26%Cr, Cu-8%Cr-1%Al, NiAl and NiCrAlY monolithic coatings were fabricated by vacuum plasma spray deposition processes for thermal expansion property measurements between 293 and 1223 K. The corrected thermal expansion, (DL/L(sub 0) varies with the absolute temperature, T, as (DL/L(sub 0) = A(T - 293)(sup 3) + BIT - 293)(sup 2) + C(T - 293) + D, where, A, B, C and D are thermal, regression constants. Excellent reproducibility was observed for all of the coatings except for data obtained on the Cu-8%Cr and Cu-26%Cr coatings in the first heat-up cycle, which deviated from those determined in the subsequent cycles. This deviation is attributed to the presence of residual stresses developed during the spraying of the coatings, which are relieved after the first heat-up cycle. In the cases of Cu-8%Cr and NiAl, the thermal expansion data were observed to be reproducible for three specimens. The linear expansion data for Cu-8% Cr and Cu-26%Cr agree extremely well with rule of mixture (ROM) predictions. Comparison of the data for the Cu-8%Cr coating with literature data for Cr and Cu revealed that the thermal expansion behavior of this alloy is determined by the Cu-rich matrix. The data for NiAl and NiCrAlY are in excellent agreement with published results irrespective of composition and the methods used for processing the materials. The implications of these results on coating GRCop-84 copper alloy combustor liners for reusable launch vehicles are discussed.

Raj, S V.↗
NASA NTRS2022

Trace Element Partitioning Between Olivine and Melt in Lunar Basalts

Mineral/melt partition coefficients have been widely used to provide insights into magmatic processes. Olivine is one of the most abundant and important minerals in the lunar mantle and mare basalts. Yet, no systematic olivine/melt partitioning data are available for lunar conditions. We report trace element partition data between host mineral olivine and its melt inclusions in lunar basalts. Equilibrium is evaluated using the Fe-Mg exchange coefficient, leading to the choice of melt inclusion-host olivine pairs in lunar basalts 12040, 12009, 15016, 15647, and 74235. Partition coefficients of 21 elements (Li, Mg, Al, Ca, Ti, V, Cr, Mn, Fe, Co, Y, Zr, Nb, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) were measured. Except for Li, V, and Cr, these elements show no significant difference in olivine-melt partitioning compared to the data for terrestrial samples. The partition coefficient of Li between olivine and melt in some lunar basalts with low Mg# (Mg# < 0.75 in olivine, or < ~0.5 in melt) is higher than published data for terrestrial * Corresponding author. Email address: youxue@umich.edu 2 samples, which is attributed to the dependence of DLi on Mg# and the lack of literature DLi data with low Mg#. The partition coefficient of V in lunar basalts is measured to be 0.17 to 0.74, significantly higher than that in terrestrial basalts (0.003 to 0.21), which can be explained by the lower oxygen fugacity in lunar basalts. The significantly higher DV can explain why V is less enriched in evolved lunar basalts than terrestrial basalts. The partition coefficient of Cr between olivine and basalt melt in the Moon is 0.11 to 0.62, which is lower than those in terrestrial settings by a factor of approximately 2. This is surprising because previous authors showed that Cr partition coefficient is independent of fO2. A quasi-thermodynamically based model is developed to correlate Cr partition coefficient to olivine and melt composition and fO2. The lower Cr partition coefficient between olivine and basalt in the Moon can lead to more Cr enrichment in the lunar magma ocean, as well as more Cr enrichment in mantle-derived basalts in the Moon. Hence, even though Cr is typically a compatible element in terrestrial basalts, it is moderately incompatible in primitive lunar basalts, with a similar degree of incompatibility as V based on partition coefficients in this work, as also evidenced by the relatively constant V/Cr ratio of 0.039 ± 0.011 in lunar basalts. The confirmation of constant V/Cr ratio is important for constraining concentrations of Cr (slightly volatile and siderophile) and V (slightly siderophile) in the bulk silicate Moon.

partition coefficients↗
DOE OSTI2020

Materials Data on Cr5B3 by Materials Project

Cr5B3 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a 5-coordinate geometry to five B atoms. There are a spread of Cr–B bond distances ranging from 2.16–2.27 Å. In the second Cr site, Cr is bonded in a 6-coordinate geometry to six B atoms. There are four shorter (2.18 Å) and two longer (2.49 Å) Cr–B bond lengths. There are two inequivalent B sites. In the first B site, B is bonded in a 10-coordinate geometry to ten Cr atoms. In the second B site, B is bonded in a 9-coordinate geometry to eight Cr and one B atom. The B–B bond length is 1.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Gd(Al2Cr)4 by Materials Project

Gd(CrAl2)4 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Gd is bonded in a 12-coordinate geometry to eight equivalent Cr and twelve Al atoms. All Gd–Cr bond lengths are 3.41 Å. There are four shorter (3.03 Å) and eight longer (3.21 Å) Gd–Al bond lengths. Cr is bonded to two equivalent Gd, two equivalent Cr, and eight Al atoms to form distorted CrGd2Al8Cr2 cuboctahedra that share corners with eight equivalent AlGd2Al6Cr4 cuboctahedra, corners with ten equivalent CrGd2Al8Cr2 cuboctahedra, edges with four equivalent CrGd2Al8Cr2 cuboctahedra, edges with four equivalent AlGd2Al6Cr4 cuboctahedra, faces with six equivalent CrGd2Al8Cr2 cuboctahedra, and faces with eight equivalent AlGd2Al6Cr4 cuboctahedra. Both Cr–Cr bond lengths are 2.52 Å. There are four shorter (2.58 Å) and four longer (2.69 Å) Cr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to two equivalent Gd, four equivalent Cr, and six Al atoms to form distorted AlGd2Al6Cr4 cuboctahedra that share corners with eight equivalent CrGd2Al8Cr2 cuboctahedra, corners with ten equivalent AlGd2Al6Cr4 cuboctahedra, edges with three equivalent AlGd2Al6Cr4 cuboctahedra, edges with four equivalent CrGd2Al8Cr2 cuboctahedra, faces with seven equivalent AlGd2Al6Cr4 cuboctahedra, and faces with eight equivalent CrGd2Al8Cr2 cuboctahedra. There are a spread of Al–Al bond distances ranging from 2.73–2.88 Å. In the second Al site, Al is bonded in a 10-coordinate geometry to one Gd, four equivalent Cr, and five Al atoms. The Al–Al bond length is 2.90 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr2As by Materials Project

Cr2As crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Cr sites. In the first Cr site, Cr is bonded in a 5-coordinate geometry to five As atoms. There are one shorter (2.56 Å) and four longer (2.67 Å) Cr–As bond lengths. In the second Cr site, Cr is bonded to four As atoms to form a mixture of distorted edge and corner-sharing CrAs4 tetrahedra. There are two shorter (2.42 Å) and two longer (2.45 Å) Cr–As bond lengths. There are two inequivalent As sites. In the first As site, As is bonded in a 9-coordinate geometry to nine Cr atoms. In the second As site, As is bonded in a 9-coordinate geometry to nine Cr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr3Se4 by Materials Project

Cr3Se4 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Cr+2.67+ sites. In the first Cr+2.67+ site, Cr+2.67+ is bonded to six Se2- atoms to form a mixture of corner, edge, and face-sharing CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–52°. There are two shorter (2.60 Å) and four longer (2.62 Å) Cr–Se bond lengths. In the second Cr+2.67+ site, Cr+2.67+ is bonded to six Se2- atoms to form a mixture of corner, edge, and face-sharing CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–52°. There are a spread of Cr–Se bond distances ranging from 2.51–2.66 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to five Cr+2.67+ atoms to form a mixture of distorted corner and edge-sharing SeCr5 trigonal bipyramids. In the second Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Cr+2.67+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y(Al2Cr)4 by Materials Project

Al8Cr4Y crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Y is bonded in a 12-coordinate geometry to eight equivalent Cr and twelve Al atoms. All Y–Cr bond lengths are 3.40 Å. There are four shorter (3.01 Å) and eight longer (3.21 Å) Y–Al bond lengths. Cr is bonded to two equivalent Y, two equivalent Cr, and eight Al atoms to form distorted CrY2Al8Cr2 cuboctahedra that share corners with eight equivalent AlY2Al6Cr4 cuboctahedra, corners with ten equivalent CrY2Al8Cr2 cuboctahedra, edges with four equivalent CrY2Al8Cr2 cuboctahedra, edges with four equivalent AlY2Al6Cr4 cuboctahedra, faces with six equivalent CrY2Al8Cr2 cuboctahedra, and faces with eight equivalent AlY2Al6Cr4 cuboctahedra. Both Cr–Cr bond lengths are 2.53 Å. There are four shorter (2.57 Å) and four longer (2.68 Å) Cr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 10-coordinate geometry to one Y, four equivalent Cr, and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.72–2.91 Å. In the second Al site, Al is bonded to two equivalent Y, four equivalent Cr, and six Al atoms to form distorted AlY2Al6Cr4 cuboctahedra that share corners with eight equivalent CrY2Al8Cr2 cuboctahedra, corners with ten equivalent AlY2Al6Cr4 cuboctahedra, edges with three equivalent AlY2Al6Cr4 cuboctahedra, edges with four equivalent CrY2Al8Cr2 cuboctahedra, faces with seven equivalent AlY2Al6Cr4 cuboctahedra, and faces with eight equivalent CrY2Al8Cr2 cuboctahedra. Both Al–Al bond lengths are 2.81 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Th(Al2Cr)4 by Materials Project

ThCr4Al8 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Th is bonded in a 12-coordinate geometry to eight equivalent Cr and twelve Al atoms. All Th–Cr bond lengths are 3.43 Å. There are four shorter (3.11 Å) and eight longer (3.22 Å) Th–Al bond lengths. Cr is bonded to two equivalent Th, two equivalent Cr, and eight Al atoms to form distorted CrTh2Al8Cr2 cuboctahedra that share corners with eight equivalent AlTh2Al6Cr4 cuboctahedra, corners with ten equivalent CrTh2Al8Cr2 cuboctahedra, edges with four equivalent CrTh2Al8Cr2 cuboctahedra, edges with four equivalent AlTh2Al6Cr4 cuboctahedra, faces with six equivalent CrTh2Al8Cr2 cuboctahedra, and faces with eight equivalent AlTh2Al6Cr4 cuboctahedra. Both Cr–Cr bond lengths are 2.51 Å. There are four shorter (2.59 Å) and four longer (2.72 Å) Cr–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to two equivalent Th, four equivalent Cr, and six Al atoms to form distorted AlTh2Al6Cr4 cuboctahedra that share corners with eight equivalent CrTh2Al8Cr2 cuboctahedra, corners with ten equivalent AlTh2Al6Cr4 cuboctahedra, edges with three equivalent AlTh2Al6Cr4 cuboctahedra, edges with four equivalent CrTh2Al8Cr2 cuboctahedra, faces with seven equivalent AlTh2Al6Cr4 cuboctahedra, and faces with eight equivalent CrTh2Al8Cr2 cuboctahedra. There are two shorter (2.74 Å) and four longer (2.86 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a 10-coordinate geometry to one Th, four equivalent Cr, and five Al atoms. The Al–Al bond length is 2.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr2HO4 by Materials Project

Cr2HO4 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. there are two inequivalent Cr+3.50+ sites. In the first Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form edge-sharing CrO6 octahedra. There is two shorter (1.94 Å) and four longer (2.02 Å) Cr–O bond length. In the second Cr+3.50+ site, Cr+3.50+ is bonded to six O2- atoms to form edge-sharing CrO6 octahedra. There are four shorter (1.97 Å) and two longer (2.04 Å) Cr–O bond lengths. H1+ is bonded in a linear geometry to two equivalent O2- atoms. Both H–O bond lengths are 1.21 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Cr+3.50+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Cr+3.50+ and one H1+ atom.

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