Materials Data on Ba5Mg18Si13 by Materials Project

Abstract

Ba5Mg18Si13 crystallizes in the hexagonal P-62m space group. The structure is three-dimensional. there are two inequivalent Ba sites. In the first Ba site, Ba is bonded in a 8-coordinate geometry to eight Mg and eight Si atoms. There are a spread of Ba–Mg bond distances ranging from 3.55–3.84 Å. There are a spread of Ba–Si bond distances ranging from 3.38–3.57 Å. In the second Ba site, Ba is bonded in a 6-coordinate geometry to nine Mg and six equivalent Si atoms. There are six shorter (3.67 Å) and three longer (3.71 Å) Ba–Mg bond lengths. All Ba–Si bond lengths are 3.46 Å. There are four inequivalent Mg sites. In the first Mg site, Mg is bonded to three Ba and four Si atoms to form distorted MgBa3Si4 tetrahedra that share corners with nine MgBa3Si4 tetrahedra, edges with six MgBa3Si4 tetrahedra, and faces with five MgBa2Si4 tetrahedra. There are a spread of Mg–Si bond distances ranging from 2.75–2.83 Å. In the second Mg site, Mg is bonded to two equivalent Ba and four Si atoms to form a mixture of distorted face, edge, and corner-sharing MgBa2Si4 tetrahedra. There are two shorter (2.68 Å) and two longer (2.78 Å) Mg–Si bond lengths. In the third Mg site, Mg is bonded to three Ba and four Si atoms to form a mixture of distorted face, edge, and corner-sharing MgBa3Si4 tetrahedra. There are a spread of Mg–Si bond distances ranging from 2.77–2.83 Å. In the fourth Mg site, Mg is bonded in a distorted single-bond geometry to five Si atoms. There are one shorter (2.73 Å) and four longer (3.16 Å) Mg–Si bond lengths. There are four inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to two equivalent Ba and seven Mg atoms. In the second Si site, Si is bonded in a 9-coordinate geometry to two equivalent Ba and seven Mg atoms. In the third Si site, Si is bonded in a 9-coordinate geometry to six equivalent Ba and three equivalent Si atoms. All Si–Si bond lengths are 2.42 Å. In the fourth Si site, Si is bonded in a 9-coordinate geometry to four equivalent Ba, four Mg, and one Si atom.