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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on HfAs2 by Materials Project

HfAs2 is Cotunnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Hf4+ is bonded in a 9-coordinate geometry to nine As2- atoms. There are a spread of Hf–As bond distances ranging from 2.77–2.97 Å. There are two inequivalent As2- sites. In the first As2- site, As2- is bonded in a 8-coordinate geometry to four equivalent Hf4+ and four As2- atoms. There are two shorter (2.60 Å) and two longer (2.92 Å) As–As bond lengths. In the second As2- site, As2- is bonded in a 7-coordinate geometry to five equivalent Hf4+ and two equivalent As2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf3As by Materials Project

Hf3As crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are six inequivalent Hf sites. In the first Hf site, Hf is bonded in a distorted see-saw-like geometry to four As atoms. There are a spread of Hf–As bond distances ranging from 2.77–2.82 Å. In the second Hf site, Hf is bonded in a distorted see-saw-like geometry to four As atoms. There are a spread of Hf–As bond distances ranging from 2.77–2.81 Å. In the third Hf site, Hf is bonded in a distorted water-like geometry to two As atoms. There are one shorter (2.77 Å) and one longer (2.97 Å) Hf–As bond lengths. In the fourth Hf site, Hf is bonded in a distorted bent 150 degrees geometry to two As atoms. There are one shorter (2.77 Å) and one longer (2.86 Å) Hf–As bond lengths. In the fifth Hf site, Hf is bonded in a 3-coordinate geometry to three As atoms. There are a spread of Hf–As bond distances ranging from 2.72–2.98 Å. In the sixth Hf site, Hf is bonded in a 3-coordinate geometry to three As atoms. There are a spread of Hf–As bond distances ranging from 2.74–2.95 Å. There are two inequivalent As sites. In the first As site, As is bonded in a 9-coordinate geometry to nine Hf atoms. In the second As site, As is bonded in a 9-coordinate geometry to nine Hf atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on HfAs by Materials Project

HfAs is Molybdenum Carbide MAX Phase-like structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to six As atoms to form a mixture of face, edge, and corner-sharing HfAs6 octahedra. The corner-sharing octahedra tilt angles range from 0–46°. There are three shorter (2.65 Å) and three longer (2.78 Å) Hf–As bond lengths. There are two inequivalent As sites. In the first As site, As is bonded to six equivalent Hf atoms to form a mixture of distorted edge and corner-sharing AsHf6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 4°. In the second As site, As is bonded to six equivalent Hf atoms to form a mixture of edge and corner-sharing AsHf6 octahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hf3As2 by Materials Project

Hf3As2 is Stibnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are three inequivalent Hf sites. In the first Hf site, Hf is bonded in a 5-coordinate geometry to five As atoms. There are a spread of Hf–As bond distances ranging from 2.72–2.80 Å. In the second Hf site, Hf is bonded to five As atoms to form edge-sharing HfAs5 square pyramids. There are a spread of Hf–As bond distances ranging from 2.68–2.73 Å. In the third Hf site, Hf is bonded in a 5-coordinate geometry to five As atoms. There are a spread of Hf–As bond distances ranging from 2.71–3.12 Å. There are two inequivalent As sites. In the first As site, As is bonded to seven Hf atoms to form a mixture of distorted corner and edge-sharing AsHf7 pentagonal bipyramids. In the second As site, As is bonded in a 8-coordinate geometry to eight Hf atoms.

36 MATERIALS SCIENCE↗