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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KMgSb by Materials Project

KMgSb is Matlockite structured and crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. K1+ is bonded to five equivalent Sb3- atoms to form distorted KSb5 trigonal bipyramids that share corners with twelve equivalent MgSb4 tetrahedra, corners with four equivalent KSb5 trigonal bipyramids, edges with four equivalent MgSb4 tetrahedra, and edges with eight equivalent KSb5 trigonal bipyramids. There are four shorter (3.65 Å) and one longer (3.75 Å) K–Sb bond lengths. Mg2+ is bonded to four equivalent Sb3- atoms to form MgSb4 tetrahedra that share corners with four equivalent MgSb4 tetrahedra, corners with twelve equivalent KSb5 trigonal bipyramids, edges with four equivalent MgSb4 tetrahedra, and edges with four equivalent KSb5 trigonal bipyramids. All Mg–Sb bond lengths are 2.95 Å. Sb3- is bonded in a 9-coordinate geometry to five equivalent K1+ and four equivalent Mg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on KMg6Sb by Materials Project

KMg6Sb crystallizes in the orthorhombic Amm2 space group. The structure is three-dimensional. K is bonded to ten Mg and two equivalent Sb atoms to form KMg10Sb2 cuboctahedra that share corners with four equivalent SbK2Mg10 cuboctahedra, corners with six equivalent KMg10Sb2 cuboctahedra, corners with eight equivalent MgK2Mg8Sb2 cuboctahedra, edges with two equivalent SbK2Mg10 cuboctahedra, edges with four equivalent MgK2Mg8Sb2 cuboctahedra, faces with two equivalent KMg10Sb2 cuboctahedra, faces with two equivalent SbK2Mg10 cuboctahedra, and faces with four equivalent MgK2Mg8Sb2 cuboctahedra. There are a spread of K–Mg bond distances ranging from 3.30–3.42 Å. Both K–Sb bond lengths are 3.31 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded to two equivalent K, eight Mg, and two equivalent Sb atoms to form distorted MgK2Mg8Sb2 cuboctahedra that share corners with four equivalent KMg10Sb2 cuboctahedra, corners with four equivalent SbK2Mg10 cuboctahedra, corners with ten equivalent MgK2Mg8Sb2 cuboctahedra, edges with two equivalent KMg10Sb2 cuboctahedra, edges with two equivalent MgK2Mg8Sb2 cuboctahedra, edges with two equivalent SbK2Mg10 cuboctahedra, faces with two equivalent KMg10Sb2 cuboctahedra, faces with two equivalent SbK2Mg10 cuboctahedra, and faces with four equivalent MgK2Mg8Sb2 cuboctahedra. There are a spread of Mg–Mg bond distances ranging from 3.24–3.34 Å. There are one shorter (3.38 Å) and one longer (3.44 Å) Mg–Sb bond lengths. In the second Mg site, Mg is bonded in a 12-coordinate geometry to two equivalent K, two equivalent Mg, and two equivalent Sb atoms. Both Mg–Sb bond lengths are 3.25 Å. In the third Mg site, Mg is bonded in a 2-coordinate geometry to two equivalent K and four equivalent Mg atoms. In the fourth Mg site, Mg is bonded in a distorted water-like geometry to four equivalent Mg and two equivalent Sb atoms. Both Mg–Sb bond lengths are 3.33 Å. Sb is bonded to two equivalent K and ten Mg atoms to form SbK2Mg10 cuboctahedra that share corners with four equivalent KMg10Sb2 cuboctahedra, corners with six equivalent SbK2Mg10 cuboctahedra, corners with eight equivalent MgK2Mg8Sb2 cuboctahedra, edges with two equivalent KMg10Sb2 cuboctahedra, edges with four equivalent MgK2Mg8Sb2 cuboctahedra, faces with two equivalent KMg10Sb2 cuboctahedra, faces with two equivalent SbK2Mg10 cuboctahedra, and faces with four equivalent MgK2Mg8Sb2 cuboctahedra.

36 MATERIALS SCIENCE↗