Materials Data on HfFeSi2 by Materials Project
HfFeSi2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Hf sites. In the first Hf site, Hf is bonded in a 1-coordinate geometry to three Fe and eight Si atoms. There are one shorter (2.28 Å) and two longer (2.91 Å) Hf–Fe bond lengths. There are a spread of Hf–Si bond distances ranging from 2.72–3.27 Å. In the second Hf site, Hf is bonded in a 7-coordinate geometry to four Fe and seven Si atoms. All Hf–Fe bond lengths are 3.06 Å. There are a spread of Hf–Si bond distances ranging from 2.66–3.13 Å. In the third Hf site, Hf is bonded in a 1-coordinate geometry to three Fe and eight Si atoms. There are one shorter (2.28 Å) and two longer (2.91 Å) Hf–Fe bond lengths. There are a spread of Hf–Si bond distances ranging from 2.72–3.28 Å. There are five inequivalent Fe sites. In the first Fe site, Fe is bonded to four Hf, two equivalent Fe, and six Si atoms to form distorted FeHf4Fe2Si6 cuboctahedra that share corners with four FeHf4Fe2Si6 cuboctahedra, corners with two equivalent FeHf2Si4 octahedra, edges with two equivalent FeHf4Fe2Si6 cuboctahedra, and faces with four FeHf4Fe2Si6 cuboctahedra. The corner-sharing octahedral tilt angles are 26°. Both Fe–Fe bond lengths are 2.55 Å. There are a spread of Fe–Si bond distances ranging from 2.37–2.41 Å. In the second Fe site, Fe is bonded to two Hf and four Si atoms to form distorted FeHf2Si4 octahedra that share corners with four FeHf4Fe2Si6 cuboctahedra and edges with two equivalent FeHf2Si4 octahedra. There are two shorter (2.29 Å) and two longer (2.34 Å) Fe–Si bond lengths. In the third Fe site, Fe is bonded to four Hf, two equivalent Fe, and six Si atoms to form distorted FeHf4Fe2Si6 cuboctahedra that share corners with four FeHf4Fe2Si6 cuboctahedra, corners with two equivalent FeHf2Si4 octahedra, edges with two equivalent FeHf4Fe2Si6 cuboctahedra, and faces with four FeHf4Fe2Si6 cuboctahedra. The corner-sharing octahedral tilt angles are 26°. Both Fe–Fe bond lengths are 2.55 Å. There are a spread of Fe–Si bond distances ranging from 2.37–2.41 Å. In the fourth Fe site, Fe is bonded to four Hf, two equivalent Fe, and six Si atoms to form distorted FeHf4Fe2Si6 cuboctahedra that share corners with four FeHf4Fe2Si6 cuboctahedra, corners with two equivalent FeHf2Si4 octahedra, edges with two equivalent FeHf4Fe2Si6 cuboctahedra, and faces with four FeHf4Fe2Si6 cuboctahedra. The corner-sharing octahedral tilt angles are 26°. There are a spread of Fe–Si bond distances ranging from 2.37–2.41 Å. In the fifth Fe site, Fe is bonded to four Hf, two equivalent Fe, and six Si atoms to form distorted FeHf4Fe2Si6 cuboctahedra that share corners with four FeHf4Fe2Si6 cuboctahedra, corners with two equivalent FeHf2Si4 octahedra, edges with two equivalent FeHf4Fe2Si6 cuboctahedra, and faces with four FeHf4Fe2Si6 cuboctahedra. The corner-sharing octahedral tilt angles are 26°. There are a spread of Fe–Si bond distances ranging from 2.37–2.41 Å. There are six inequivalent Si sites. In the first Si site, Si is bonded in a 3-coordinate geometry to four Hf, two equivalent Fe, and two equivalent Si atoms. There are one shorter (2.52 Å) and one longer (2.58 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 7-coordinate geometry to three Hf and four Fe atoms. In the third Si site, Si is bonded in a 12-coordinate geometry to four Hf and four Fe atoms. In the fourth Si site, Si is bonded in a 10-coordinate geometry to six Hf, two equivalent Fe, and two equivalent Si atoms. There are one shorter (2.46 Å) and one longer (2.64 Å) Si–Si bond lengths. In the fifth Si site, Si is bonded in a 6-coordinate geometry to three Hf, two Fe, and one Si atom. The Si–Si bond length is 2.33 Å. In the sixth Si site, Si is bonded in a 6-coordinate geometry to three Hf, two Fe, and one Si atom.