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Published in Zbigniew Galazka, Transparent Semiconducting Oxides, 2020
In2O3 crystallizes in a body-centered cubic structure (space group Ia3 ), which is named after the mineral bixbyite (Fe,Mn)2O3. The structure can be derived from the fluorite (CaF2 = ½Ca2F4) structure by removing one-quarter of the anions and a subsequent shift in the remaining ions [99]. As a consequence of this shift, the cations are surrounded by distorted octahedra. Three-fourths of the cations are on the Wyckoff position d (site symmetry 2) and one-fourth on the Wyckoff position b (site symmetry з̄); these positions are marked in Fig. 5.1 by blue or red circles, respectively. It results in two inequivalent In sites In1 (¼, ¼, ¼), and In2 (u, O, ½) and one O site. Both In1 and In2 are six-fold coordinated, surrounded by O atoms, while all O atoms are four-fold coordinated to In atoms. The local structure of In1 is highly symmetric, while the local structure of In2 is less symmetric. The local structure of O forms a distorted tetrahedron with all four In–O bonds inequivalent [100]. Indeed, the refined crystal structure given by Marezio [101] revealed equal In1–O bond lengths of 2.18 Å, and different In2–O bond lengths of 2.13, 2.19, and 2.23 Å. The measured lattice parameter of a single crystal is 10.117 ± 0.001 Å. The In2O3structure contains 80 atoms in a unit cell.
Machine learning prediction on intermetallic compounds with implemented virtual-center-atom structural descriptor
Published in Science and Technology of Advanced Materials: Methods, 2022
For periodic system, the VCA descriptor calculation for structures is equivalent to finding the high-symmetric center of the crystal. The virtual center can be found via a four-step atomic labeling and calculation: To calculate the Wyckoff positions of the primitive cell under a Bravais lattice symmetry.To build sublattices with origin on each of the atoms in Wyckoff position lists.VCA centers are calculated as centers of the atomic configurations enclosed within each of the re-defined unit cells.Practical VCA center is at the averaged position of the above VCA centers.