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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Molecular dynamics simulations of radiation response of $\mathrm{LiAlO_2}$ and $\mathrm{LiAl_5O_8}$

Here, we report the findings of a computational investigation of defect production and migration in two lithium aluminate ceramics: LiAlO 2 and LiAl 5 O 8 . Although the first ceramic, LiAlO 2 has been widely investigated computationally, especially via molecular dynamics (MD), there have been no MD studies done on LiAl 5 O 8 up to date, due to the lack of interatomic potentials for this system. This work implemented an existing set of Li-Al-O coulombic and Buckingham potential parameters for the LiAl 5 O 8 system from the literature, followed by validating it based on experimental values of density, crystallinity, bond lengths and melting point. The Li + diffusion in the two ceramics was examined and was found to be one order of magnitude slower in LiAl 5 O 8 (D 0 = 3.17 x 10 -11 m 2 /s) as compared to that in LiAlO 2 (D 0 = 4.02 x 10 -10 m 2 /s) at 600 K. The lithium vacancy migration barrier of 4.15 eV in LiAl 5 O 8 was more than three times that in LiAlO 2 (1.31 eV) possibly due to stronger ordering in the Li-O 6 octahedra of LiAl 5 O 8 than in Li-O 4 tetrahedra of LiAlO 2 . The Li displacement threshold energy (E d ) in LiAl 5 O 8 was found to have a median value of 68 eV which is much higher than that in LiAlO 2 (40 eV). The greater E d for Li signifies a lower likelihood for defect formation and clustering and thus lower tendency for amorphization in LiAl 5 O 8 . The presented results show the difference in defect dynamics in the two ceramics that may help us understand the susceptibility of the two ceramics to amorphization caused by irradiation.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(H2N)4 by Materials Project

LiAl(NH2)4 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of eight hydrogen molecules and one LiAl(NH)4 sheet oriented in the (1, 0, 0) direction. In the LiAl(NH)4 sheet, Li1+ is bonded in a distorted tetrahedral geometry to four N3- atoms. There are a spread of Li–N bond distances ranging from 2.01–2.12 Å. Al3+ is bonded in a 4-coordinate geometry to four N3- atoms. There are a spread of Al–N bond distances ranging from 1.86–1.89 Å. There are four inequivalent N3- sites. In the first N3- site, N3- is bonded to one Li1+, one Al3+, and two H1+ atoms to form distorted corner-sharing NLiAlH2 tetrahedra. There is one shorter (1.02 Å) and one longer (1.03 Å) N–H bond length. In the second N3- site, N3- is bonded in a 3-coordinate geometry to one Li1+, one Al3+, and one N3- atom. The N–N bond length is 1.28 Å. In the third N3- site, N3- is bonded in a 3-coordinate geometry to one Li1+, one Al3+, and one N3- atom. In the fourth N3- site, N3- is bonded to one Li1+, one Al3+, and two H1+ atoms to form distorted corner-sharing NLiAlH2 tetrahedra. Both N–H bond lengths are 1.02 Å. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one N3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A New Complex Borohydride LiAl(BH4)2Cl2

A new mixed alkali metal–aluminum borohydride LiAl(BH4)2Cl2 has been prepared via mechanochemical synthesis from the 2LiBH4–AlCl3 mixture. Structural characterization, performed using a combination of X-ray powder diffraction and solid-state NMR methods, indicates that the LiAl(BH4)2Cl2 phase adopts a unique 3D framework and crystallizes in an orthorhombic structure with the space group C2221, a = 11.6709(6) Å, b = 8.4718(4) Å, c = 7.5114(3) Å. The material shows excellent dehydrogenation characteristics, where hydrogen evolution starts at Tons = 70 °C, releasing approximately 2 wt.% of nearly pure (99.8 vol.%) hydrogen and a very small amount (~0.2 vol.%) of diborane. When compared to halide-free mixed alkali metal–aluminum borohydrides, the presence of Al‒Cl bonding in the LiAl(BH4)2Cl2 structure likely prevents the formation of Al(BH4)3 upon decomposition, thus suppressing the formation of diborane.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

First-principles study of the surface properties of LiAl 5 O 8 : Stability and tritiated water formation

LiAl 5 O 8 is an important secondary phase of γ-LiAlO 2 ceramics in tritium ( 3 H, T)-producing burnable absorber rods (TPBARs), present in small quantities in the as-fabricated condition and in larger quantities after irradiation due to Li burnup and mobility in the radiation-damaged lattice. In this work, we performed first-principles calculations to study the stabilities and structures of LiAl 5 O 8 surfaces the possibility of T 2 O formation on the (111) surface. By calculating the surface energies of all possible symmetrical stoichiometric and nonstoichiometric low-index surfaces, we identified the two most stable surfaces, one stoichiometric (001) surface and one nonstoichiometric (111) surface in an O-rich condition. The surface oxygen atoms on the nonstoichiometric (111) surface have remarkable displacements after relaxation, due to the large dangling O bonds. Considering a Li-poor and 3 H-rich condition relevant to TPBARs, we further studied these two stable surfaces with 37.5%, 75%, and 100% surface O atoms covered by 3 H atoms. Our results show that the 3H saturation is favorable for the nonstoichiometric (111) surface but not for the stoichiometric (001) surface. In addition, the structure of nonstoichiometric (111) surface is well stabilized when the surface O atoms are 100% saturated by 3 H atoms. Based on the fully 3H-saturated (111) surface, the 3 H 2 O desorption with an energy barrier of 0.69 eV is preferable in the 3 H-rich condition.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(PS3)2 by Materials Project

LiAl(PS3)2 crystallizes in the monoclinic C2/c space group. The structure is two-dimensional and consists of two LiAl(PS3)2 sheets oriented in the (0, 0, 1) direction. Li1+ is bonded to six S2- atoms to form LiS6 octahedra that share edges with three equivalent AlS6 octahedra. There are a spread of Li–S bond distances ranging from 2.67–2.71 Å. Al3+ is bonded to six S2- atoms to form AlS6 octahedra that share edges with three equivalent LiS6 octahedra. There are a spread of Al–S bond distances ranging from 2.43–2.48 Å. P4+ is bonded in a trigonal non-coplanar geometry to three S2- atoms. There are two shorter (2.04 Å) and one longer (2.05 Å) P–S bond lengths. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one P4+ atom. In the second S2- site, S2- is bonded in a 3-coordinate geometry to one Li1+, one Al3+, and one P4+ atom. In the third S2- site, S2- is bonded in a 3-coordinate geometry to one Li1+, one Al3+, and one P4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Molecular dynamics study of grain boundaries as defect sinks under irradiation in LiAlO 2 and LiAl 5 O 8

Lithium aluminate ceramics, LiAlO 2 and LiAl 5 O 8 , show promise in nuclear environments due to their excellent radiation tolerance. Molecular dynamics simulations investigate grain boundaries (GB) and their role in defect evolution. Results reveal that GBs act as efficient defect sinks, with Li and Al atoms exhibiting distinct behaviors during displacement cascades. Tritium migration in LiAlO 2 is also studied, showing rapid diffusion and stable configurations with oxygen, corroborated by ab initio simulations from the literature. The calculated tritium diffusion coefficient of 1.33 × 10 - ¹⁴ m²/s aligns with the literature, validating the model. LiAl 5 O 8 demonstrates superior defect healing compared to LiAlO 2 , attributed to enhanced atomic transfer between grains and GBs. These findings reveal key insights into defect dynamics, providing essential insights for their application in tritium-producing burnable absorber rods (TPBARs).

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(MoO4)2 by Materials Project

LiAl(MoO4)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Li1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Li–O bond distances ranging from 1.98–2.25 Å. There are two inequivalent Mo6+ sites. In the first Mo6+ site, Mo6+ is bonded in a 4-coordinate geometry to five O2- atoms. There are a spread of Mo–O bond distances ranging from 1.74–2.46 Å. In the second Mo6+ site, Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 15–44°. There are a spread of Mo–O bond distances ranging from 1.77–1.82 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MoO4 tetrahedra and an edgeedge with one AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.95 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Mo6+, and one Al3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mo6+ and two equivalent Al3+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Li1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a linear geometry to one Li1+ and one Mo6+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to one Mo6+ and one Al3+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Li1+ and one Mo6+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to one Li1+, two equivalent Mo6+, and one Al3+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Mo6+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(PO3)4 by Materials Project

LiAl(PO3)4 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Li1+ is bonded to four O2- atoms to form distorted LiO4 tetrahedra that share corners with four equivalent PO4 tetrahedra and an edgeedge with one AlO6 octahedra. There is two shorter (1.92 Å) and two longer (2.07 Å) Li–O bond length. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six PO4 tetrahedra and an edgeedge with one LiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.89–1.92 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two equivalent LiO4 tetrahedra, and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. There are a spread of P–O bond distances ranging from 1.48–1.62 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent AlO6 octahedra and corners with two equivalent PO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–47°. There are a spread of P–O bond distances ranging from 1.50–1.60 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two P5+ atoms. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Al3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Li1+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Al3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Li1+, one Al3+, and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(Si2O5)2 by Materials Project

LiAl(Si2O5)2 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four O2- atoms. There is two shorter (1.97 Å) and two longer (1.98 Å) Li–O bond length. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra. All Al–O bond lengths are 1.75 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.62 Å) and two longer (1.63 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.62 Å) and two longer (1.63 Å) Si–O bond length. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(Si2O5)2 by Materials Project

LiAl(Si2O5)2 crystallizes in the monoclinic Pc space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of Li–O bond distances ranging from 1.95–1.99 Å. Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra. There is two shorter (1.75 Å) and two longer (1.76 Å) Al–O bond length. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.62 Å) and two longer (1.63 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is two shorter (1.62 Å) and two longer (1.63 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the ninth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom. In the tenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl by Materials Project

LiAl crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Li is bonded in a 11-coordinate geometry to four equivalent Li and seven Al atoms. There are one shorter (2.86 Å) and three longer (2.95 Å) Li–Li bond lengths. There are one shorter (2.87 Å) and six longer (2.95 Å) Li–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to six equivalent Li and three equivalent Al atoms. All Al–Al bond lengths are 2.58 Å. In the second Al site, Al is bonded in a 11-coordinate geometry to eight equivalent Li and three equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(CN2)2 by Materials Project

LiAl(CN2)2 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. Li1+ is bonded to six N3- atoms to form LiN6 octahedra that share edges with two equivalent LiN6 octahedra and edges with four equivalent AlN6 octahedra. There are a spread of Li–N bond distances ranging from 2.28–2.34 Å. Al3+ is bonded to six N3- atoms to form AlN6 octahedra that share edges with two equivalent AlN6 octahedra and edges with four equivalent LiN6 octahedra. There are a spread of Al–N bond distances ranging from 2.00–2.05 Å. C4+ is bonded in a linear geometry to two N3- atoms. There is one shorter (1.21 Å) and one longer (1.25 Å) C–N bond length. There are two inequivalent N3- sites. In the first N3- site, N3- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Li1+, one Al3+, and one C4+ atom. In the second N3- site, N3- is bonded to one Li1+, two equivalent Al3+, and one C4+ atom to form a mixture of distorted corner and edge-sharing NLiAl2C trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl by Materials Project

LiAl crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are three inequivalent Li sites. In the first Li site, Li is bonded to four equivalent Al atoms to form distorted edge-sharing LiAl4 tetrahedra. There are two shorter (2.85 Å) and two longer (2.88 Å) Li–Al bond lengths. In the second Li site, Li is bonded in a 6-coordinate geometry to four Al atoms. There are two shorter (2.79 Å) and two longer (2.81 Å) Li–Al bond lengths. In the third Li site, Li is bonded in a 6-coordinate geometry to six Al atoms. There are a spread of Li–Al bond distances ranging from 2.77–2.98 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to four Li and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.55–2.70 Å. In the second Al site, Al is bonded in a 5-coordinate geometry to five Li and two equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(SiO3)2 by Materials Project

LiAlSi2O6 is Esseneite-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.09–2.56 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–2.05 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 27–60°. There are a spread of Si–O bond distances ranging from 1.60–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–58°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Li1+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Li1+ and two equivalent Si4+ atoms. In the third O2- site, O2- is bonded to one Li1+, two equivalent Al3+, and one Si4+ atom to form a mixture of distorted edge and corner-sharing OLiAl2Si trigonal pyramids. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+ and two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded to one Li1+, two equivalent Al3+, and one Si4+ atom to form a mixture of distorted edge and corner-sharing OLiAl2Si trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(SiO3)2 by Materials Project

LiAlSi2O6 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are two inequivalent Li1+ sites. In the first Li1+ site, Li1+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is two shorter (1.93 Å) and one longer (1.94 Å) Li–O bond length. In the second Li1+ site, Li1+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are a spread of Li–O bond distances ranging from 1.91–1.94 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.72–1.79 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four SiO4 tetrahedra. There is one shorter (1.72 Å) and three longer (1.78 Å) Al–O bond length. There are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There is one shorter (1.61 Å) and three longer (1.64 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There is one shorter (1.63 Å) and three longer (1.64 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with three SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.60–1.64 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one SiO4 tetrahedra and corners with three AlO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Al3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Al3+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Al3+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Al3+, and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a trigonal planar geometry to one Li1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(SiO3)2 by Materials Project

LiAlSi2O6 is Esseneite structured and crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Li1+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Li–O bond distances ranging from 2.11–2.30 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–2.03 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 30–60°. There are a spread of Si–O bond distances ranging from 1.60–1.66 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded to one Li1+, two equivalent Al3+, and one Si4+ atom to form a mixture of distorted corner and edge-sharing OLiAl2Si tetrahedra. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Li1+, one Al3+, and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl(GeO3)2 by Materials Project

LiAlGe2O6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Li1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Li–O bond distances ranging from 2.05–2.18 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent GeO4 tetrahedra, corners with two equivalent GeO5 trigonal bipyramids, edges with two equivalent AlO6 octahedra, and an edgeedge with one GeO5 trigonal bipyramid. There are a spread of Al–O bond distances ranging from 1.84–2.03 Å. There are two inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to five O2- atoms to form distorted GeO5 trigonal bipyramids that share corners with two equivalent AlO6 octahedra, corners with three equivalent GeO4 tetrahedra, and an edgeedge with one AlO6 octahedra. The corner-sharing octahedra tilt angles range from 25–51°. There are a spread of Ge–O bond distances ranging from 1.74–2.39 Å. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent AlO6 octahedra and corners with three equivalent GeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 46–67°. There are a spread of Ge–O bond distances ranging from 1.75–1.79 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded to one Li1+, two equivalent Al3+, and one Ge4+ atom to form a mixture of edge and corner-sharing OLiAl2Ge tetrahedra. In the second O2- site, O2- is bonded in a 2-coordinate geometry to one Al3+ and two Ge4+ atoms. In the third O2- site, O2- is bonded to one Li1+, two equivalent Al3+, and one Ge4+ atom to form a mixture of distorted edge and corner-sharing OLiAl2Ge tetrahedra. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Li1+ and two Ge4+ atoms. In the fifth O2- site, O2- is bonded in a T-shaped geometry to one Li1+, one Al3+, and one Ge4+ atom. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to one Li1+ and two Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Molecular dynamics simulations of displacement cascades in LiAlO2 and LiAl5O8 ceramics

Abstract Molecular dynamics was employed to investigate the radiation damage due to collision cascades in LiAlO 2 and LiAl 5 O 8 , the latter being a secondary phase formed in the former during irradiation. Atomic displacement cascades were simulated by initiating primary knock-on atoms (PKA) with energy values = 5, 10 and 15 keV and the damage was quantified by the number of Frenkel pairs formed for each species: Li, Al and O. The primary challenges of modeling an ionic system with and without a core–shell model for oxygen atoms were addressed and new findings on the radiation resistance of these ceramics are presented. The working of a variable timestep function and the kinetics in the background of the simulations have been elaborated to highlight the novelty of the simulation approach. More importantly, the key results indicated that LiAlO 2 experiences much more radiation damage than LiAl 5 O 8 , where the number of Li Frenkel pairs in LiAlO 2 was 3–5 times higher than in LiAl 5 O 8 while the number of Frenkel pairs for Al and O in LiAlO 2 are ~ 2 times higher than in LiAl 5 O 8 . The primary reason is high displacement threshold energies (E d ) in LiAl 5 O 8 for Li cations. The greater E d for Li imparts higher resistance to damage during the collision cascade and thus inhibits amorphization in LiAl 5 O 8 . The presented results suggest that LiAl 5 O 8 is likely to maintain structural integrity better than LiAlO 2 in the irradiation conditions studied in this work.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗