DOI: 10.17188/1748161
title: Materials Data on Mg5Si9 by Materials Project

description: Mg5Si9 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are ten inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to six Si atoms. There are a spread of Mg–Si bond distances ranging from 2.67–3.19 Å. In the second Mg site, Mg is bonded in a 5-coordinate geometry to five Si atoms. There are a spread of Mg–Si bond distances ranging from 2.73–2.90 Å. In the third Mg site, Mg is bonded to five Si atoms to form distorted MgSi5 trigonal bipyramids that share a cornercorner with one SiMg4Si2 octahedra, corners with two equivalent MgSi5 tetrahedra, and an edgeedge with one MgSi5 tetrahedra. The corner-sharing octahedral tilt angles are 71°. There are a spread of Mg–Si bond distances ranging from 2.70–2.95 Å. In the fourth Mg site, Mg is bonded in a 4-coordinate geometry to five Si atoms. There are a spread of Mg–Si bond distances ranging from 2.74–3.08 Å. In the fifth Mg site, Mg is bonded in a 4-coordinate geometry to seven Si atoms. There are a spread of Mg–Si bond distances ranging from 2.69–3.23 Å. In the sixth Mg site, Mg is bonded to five Si atoms to form distorted MgSi5 tetrahedra that share a cornercorner with one SiMg4Si2 octahedra, corners with two equivalent MgSi5 trigonal bipyramids, and an edgeedge with one MgSi5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 81°. There are a spread of Mg–Si bond distances ranging from 2.61–3.28 Å. In the seventh Mg site, Mg is bonded in a 8-coordinate geometry to eight Si atoms. There are a spread of Mg–Si bond distances ranging from 2.71–3.07 Å. In the eighth Mg site, Mg is bonded in a 8-coordinate geometry to eight Si atoms. There are a spread of Mg–Si bond distances ranging from 2.83–3.10 Å. In the ninth Mg site, Mg is bonded in a 6-coordinate geometry to six Si atoms. There are a spread of Mg–Si bond distances ranging from 2.68–3.03 Å. In the tenth Mg site, Mg is bonded in a 5-coordinate geometry to five Si atoms. There are a spread of Mg–Si bond distances ranging from 2.72–2.96 Å. There are eighteen inequivalent Si sites. In the first Si site, Si is bonded in a 5-coordinate geometry to one Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.40–2.49 Å. In the second Si site, Si is bonded in a 6-coordinate geometry to two Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.36–2.47 Å. In the third Si site, Si is bonded in a 6-coordinate geometry to six Mg and three Si atoms. There are a spread of Si–Si bond distances ranging from 2.44–2.68 Å. In the fourth Si site, Si is bonded in a 5-coordinate geometry to one Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.40–2.61 Å. In the fifth Si site, Si is bonded to four Mg and two Si atoms to form distorted SiMg4Si2 octahedra that share a cornercorner with one SiMg5Si2 pentagonal bipyramid, a cornercorner with one MgSi5 tetrahedra, and a cornercorner with one MgSi5 trigonal bipyramid. The Si–Si bond length is 2.39 Å. In the sixth Si site, Si is bonded in a 5-coordinate geometry to one Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.34–2.45 Å. In the seventh Si site, Si is bonded in a 1-coordinate geometry to four Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.38–2.47 Å. In the eighth Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. There are one shorter (2.42 Å) and one longer (2.44 Å) Si–Si bond lengths. In the ninth Si site, Si is bonded in a 7-coordinate geometry to three Mg and four Si atoms. There are one shorter (2.41 Å) and one longer (2.42 Å) Si–Si bond lengths. In the tenth Si site, Si is bonded to five Mg and two Si atoms to form distorted corner-sharing SiMg5Si2 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 50°. In the eleventh Si site, Si is bonded in a 1-coordinate geometry to two Mg and four Si atoms. The Si–Si bond length is 2.35 Å. In the twelfth Si site, Si is bonded in a 6-coordinate geometry to three Mg and three Si atoms. In the thirteenth Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. In the fourteenth Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. In the fifteenth Si site, Si is bonded in a 6-coordinate geometry to four Mg and two Si atoms. In the sixteenth Si site, Si is bonded in a 7-coordinate geometry to three Mg and three Si atoms. In the seventeenth Si site, Si is bonded in a 7-coordinate geometry to five Mg and two Si atoms. In the eighteenth Si site, Si is bonded in a 6-coordinate geometry to four Mg and two Si atoms.