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8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on GeSb by Materials Project

GeSb is Halite, Rock Salt structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ge3+ is bonded to six equivalent Sb3- atoms to form a mixture of corner and edge-sharing GeSb6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.90 Å) and two longer (2.94 Å) Ge–Sb bond lengths. Sb3- is bonded to six equivalent Ge3+ atoms to form a mixture of corner and edge-sharing SbGe6 octahedra. The corner-sharing octahedral tilt angles are 0°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho5(GeSb)2 by Materials Project

Ho5(GeSb)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded to three equivalent Ge and three equivalent Sb atoms to form distorted HoGe3Sb3 pentagonal pyramids that share corners with three equivalent HoGe4Sb2 octahedra, corners with ten equivalent HoGe3Sb3 pentagonal pyramids, edges with seven equivalent HoGe3Sb3 pentagonal pyramids, faces with two equivalent HoGe4Sb2 octahedra, and faces with two equivalent HoGe3Sb3 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 36–42°. There are a spread of Ho–Ge bond distances ranging from 2.93–3.08 Å. There are a spread of Ho–Sb bond distances ranging from 3.12–3.18 Å. In the second Ho site, Ho is bonded to four equivalent Ge and two equivalent Sb atoms to form HoGe4Sb2 octahedra that share corners with four equivalent HoGe4Sb2 octahedra, corners with twelve equivalent HoGe3Sb3 pentagonal pyramids, and faces with eight equivalent HoGe3Sb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 48°. There are two shorter (3.05 Å) and two longer (3.07 Å) Ho–Ge bond lengths. Both Ho–Sb bond lengths are 3.09 Å. Ge is bonded in a 8-coordinate geometry to eight Ho atoms. Sb is bonded to seven Ho atoms to form a mixture of distorted edge and corner-sharing SbHo7 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy5(GeSb)2 by Materials Project

Dy5(GeSb)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent Dy sites. In the first Dy site, Dy is bonded to three equivalent Ge and three equivalent Sb atoms to form distorted DyGe3Sb3 pentagonal pyramids that share corners with three equivalent DyGe4Sb2 octahedra, corners with ten equivalent DyGe3Sb3 pentagonal pyramids, edges with seven equivalent DyGe3Sb3 pentagonal pyramids, faces with two equivalent DyGe4Sb2 octahedra, and faces with two equivalent DyGe3Sb3 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 36–42°. There are a spread of Dy–Ge bond distances ranging from 2.94–3.09 Å. There are a spread of Dy–Sb bond distances ranging from 3.13–3.19 Å. In the second Dy site, Dy is bonded to four equivalent Ge and two equivalent Sb atoms to form DyGe4Sb2 octahedra that share corners with four equivalent DyGe4Sb2 octahedra, corners with twelve equivalent DyGe3Sb3 pentagonal pyramids, and faces with eight equivalent DyGe3Sb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 48°. There are two shorter (3.06 Å) and two longer (3.08 Å) Dy–Ge bond lengths. Both Dy–Sb bond lengths are 3.10 Å. Ge is bonded in a 8-coordinate geometry to eight Dy atoms. Sb is bonded to seven Dy atoms to form a mixture of distorted edge and corner-sharing SbDy7 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeSb by Materials Project

GeSb is High Pressure Cadmuum Telluride structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ge3+ is bonded in a linear geometry to two equivalent Sb3- atoms. Both Ge–Sb bond lengths are 2.93 Å. Sb3- is bonded to two equivalent Ge3+ and four equivalent Sb3- atoms to form a mixture of edge and corner-sharing SbGe2Sb4 octahedra. The corner-sharing octahedral tilt angles are 0°. All Sb–Sb bond lengths are 2.94 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y5(GeSb)2 by Materials Project

Y5(GeSb)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent Y sites. In the first Y site, Y is bonded to three equivalent Ge and three equivalent Sb atoms to form distorted YGe3Sb3 pentagonal pyramids that share corners with three equivalent YGe4Sb2 octahedra, corners with ten equivalent YGe3Sb3 pentagonal pyramids, edges with seven equivalent YGe3Sb3 pentagonal pyramids, faces with two equivalent YGe4Sb2 octahedra, and faces with two equivalent YGe3Sb3 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 36–42°. There are a spread of Y–Ge bond distances ranging from 2.95–3.09 Å. There are a spread of Y–Sb bond distances ranging from 3.14–3.20 Å. In the second Y site, Y is bonded to four equivalent Ge and two equivalent Sb atoms to form YGe4Sb2 octahedra that share corners with four equivalent YGe4Sb2 octahedra, corners with twelve equivalent YGe3Sb3 pentagonal pyramids, and faces with eight equivalent YGe3Sb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 48°. There are two shorter (3.07 Å) and two longer (3.09 Å) Y–Ge bond lengths. Both Y–Sb bond lengths are 3.11 Å. Ge is bonded in a 8-coordinate geometry to eight Y atoms. Sb is bonded to seven Y atoms to form a mixture of distorted edge and corner-sharing SbY7 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeSb by Materials Project

GeSb is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Ge3+ is bonded to four equivalent Sb3- atoms to form corner-sharing GeSb4 tetrahedra. All Ge–Sb bond lengths are 2.78 Å. Sb3- is bonded to four equivalent Ge3+ atoms to form corner-sharing SbGe4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Tm5(GeSb)2 by Materials Project

Tm5(GeSb)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent Tm sites. In the first Tm site, Tm is bonded to three equivalent Ge and three equivalent Sb atoms to form distorted TmGe3Sb3 pentagonal pyramids that share corners with three equivalent TmGe4Sb2 octahedra, corners with ten equivalent TmGe3Sb3 pentagonal pyramids, edges with seven equivalent TmGe3Sb3 pentagonal pyramids, faces with two equivalent TmGe4Sb2 octahedra, and faces with two equivalent TmGe3Sb3 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 36–42°. There are one shorter (2.90 Å) and two longer (3.04 Å) Tm–Ge bond lengths. There are a spread of Tm–Sb bond distances ranging from 3.09–3.15 Å. In the second Tm site, Tm is bonded to four equivalent Ge and two equivalent Sb atoms to form TmGe4Sb2 octahedra that share corners with four equivalent TmGe4Sb2 octahedra, corners with twelve equivalent TmGe3Sb3 pentagonal pyramids, and faces with eight equivalent TmGe3Sb3 pentagonal pyramids. The corner-sharing octahedral tilt angles are 48°. There are two shorter (3.02 Å) and two longer (3.04 Å) Tm–Ge bond lengths. Both Tm–Sb bond lengths are 3.07 Å. Ge is bonded in a 8-coordinate geometry to eight Tm atoms. Sb is bonded to seven Tm atoms to form a mixture of distorted corner and edge-sharing SbTm7 pentagonal bipyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Highly tunable band inversion in AB 2 X 4 (A=Ge, Sn, Pb; B=As, Sb, Bi; X=Se, Te) compounds

Topological materials have been discovered so far largely by searching for existing compounds in crystallographic databases, but there are potentially new topological materials with desirable features that have not been synthesized. One of the desirable features is high tunability resulting from the band inversion with a very small direct band gap, which can be tuned by changes in pressure or strain to induce a topological phase transition. Here, using density-functional theory (DFT) calculations, we have studied the septuple layered AB 2 X 4 series compounds, where A=(Ge, Sn and Pb), B=(As, Sb and Bi), and X=(Se and Te). With the DFT thermodynamic stability validated by the already-reported compounds in these series, we predict stable Se compounds, which are not found in crystallographic database. Among them, we find that GeBi 2 Se 4 and GeSb 2 Se 4 having a small direct band gap at the Z point are very close to a strong topological insulator, which can be tuned by a moderate pressure to induce the band inversion. Importantly, the topological features with the small direct band gap are well isolated in both momentum and energy windows, which offers high tunability for studying the topological phase transition.

36 MATERIALS SCIENCE↗