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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on GeSe2 by Materials Project

GeSe2 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of two GeSe2 sheets oriented in the (0, 0, 1) direction. there are four inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing GeSe4 tetrahedra. There are two shorter (2.40 Å) and two longer (2.41 Å) Ge–Se bond lengths. In the second Ge4+ site, Ge4+ is bonded to four Se2- atoms to form corner-sharing GeSe4 tetrahedra. There are two shorter (2.39 Å) and two longer (2.40 Å) Ge–Se bond lengths. In the third Ge4+ site, Ge4+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing GeSe4 tetrahedra. There are three shorter (2.40 Å) and one longer (2.41 Å) Ge–Se bond lengths. In the fourth Ge4+ site, Ge4+ is bonded to four Se2- atoms to form corner-sharing GeSe4 tetrahedra. There are a spread of Ge–Se bond distances ranging from 2.39–2.41 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the second Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the third Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the fourth Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the fifth Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms. In the sixth Se2- site, Se2- is bonded in a distorted L-shaped geometry to two Ge4+ atoms. In the seventh Se2- site, Se2- is bonded in a distorted L-shaped geometry to two Ge4+ atoms. In the eighth Se2- site, Se2- is bonded in a water-like geometry to two Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ni11(GeSe2)2 by Materials Project

Ni11(GeSe2)2 crystallizes in the tetragonal P4mm space group. The structure is two-dimensional and consists of one Ni11(GeSe2)2 sheet oriented in the (0, 0, 1) direction. there are seven inequivalent Ni sites. In the first Ni site, Ni is bonded in a 12-coordinate geometry to eight Ni, two equivalent Ge, and two equivalent Se atoms. There are a spread of Ni–Ni bond distances ranging from 2.52–2.65 Å. Both Ni–Ge bond lengths are 2.51 Å. Both Ni–Se bond lengths are 2.43 Å. In the second Ni site, Ni is bonded in a 2-coordinate geometry to two equivalent Ni, two equivalent Ge, and two equivalent Se atoms. Both Ni–Ni bond lengths are 2.53 Å. Both Ni–Ge bond lengths are 2.53 Å. Both Ni–Se bond lengths are 2.34 Å. In the third Ni site, Ni is bonded in a distorted water-like geometry to two equivalent Ni, two equivalent Ge, and two equivalent Se atoms. Both Ni–Ni bond lengths are 2.53 Å. Both Ni–Ge bond lengths are 2.54 Å. Both Ni–Se bond lengths are 2.34 Å. In the fourth Ni site, Ni is bonded in a 2-coordinate geometry to two equivalent Ni, two equivalent Ge, and two equivalent Se atoms. Both Ni–Ni bond lengths are 2.52 Å. Both Ni–Ge bond lengths are 2.53 Å. Both Ni–Se bond lengths are 2.34 Å. In the fifth Ni site, Ni is bonded to eight Ni and four equivalent Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with four equivalent NiNi8Ge4 cuboctahedra, edges with four equivalent NiNi4Se5 square pyramids, faces with four equivalent NiNi8Ge4 cuboctahedra, and faces with four equivalent GeNi12 cuboctahedra. All Ni–Ge bond lengths are 2.56 Å. In the sixth Ni site, Ni is bonded to eight Ni and four equivalent Ge atoms to form NiNi8Ge4 cuboctahedra that share corners with four equivalent NiNi8Ge4 cuboctahedra, faces with four equivalent NiNi8Ge4 cuboctahedra, and faces with four equivalent GeNi12 cuboctahedra. All Ni–Ge bond lengths are 2.56 Å. In the seventh Ni site, Ni is bonded to four equivalent Ni and five Se atoms to form distorted NiNi4Se5 square pyramids that share corners with four equivalent GeNi12 cuboctahedra, corners with four equivalent NiNi4Se5 square pyramids, edges with four equivalent NiNi8Ge4 cuboctahedra, a faceface with one GeNi12 cuboctahedra, and faces with four equivalent NiNi4Se5 square pyramids. There are one shorter (2.29 Å) and four longer (2.58 Å) Ni–Se bond lengths. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded to twelve Ni atoms to form GeNi12 cuboctahedra that share corners with four equivalent GeNi12 cuboctahedra, faces with four equivalent NiNi8Ge4 cuboctahedra, and faces with four equivalent GeNi12 cuboctahedra. In the second Ge site, Ge is bonded to twelve Ni atoms to form GeNi12 cuboctahedra that share corners with four equivalent GeNi12 cuboctahedra, corners with four equivalent NiNi4Se5 square pyramids, faces with four equivalent NiNi8Ge4 cuboctahedra, faces with four equivalent GeNi12 cuboctahedra, and a faceface with one NiNi4Se5 square pyramid. There are four inequivalent Se sites. In the first Se site, Se is bonded in a 8-coordinate geometry to eight Ni atoms. In the second Se site, Se is bonded in a 4-coordinate geometry to four equivalent Ni atoms. In the third Se site, Se is bonded in a 5-coordinate geometry to five Ni atoms. In the fourth Se site, Se is bonded in a 4-coordinate geometry to four equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on GeSe2 by Materials Project

GeSe2 crystallizes in the tetragonal I-42d space group. The structure is three-dimensional. Ge4+ is bonded to four equivalent Se2- atoms to form corner-sharing GeSe4 tetrahedra. All Ge–Se bond lengths are 2.40 Å. Se2- is bonded in a water-like geometry to two equivalent Ge4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(GeSe2)2 by Materials Project

K(GeSe2)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.38–3.95 Å. In the second K1+ site, K1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of K–Se bond distances ranging from 3.37–3.98 Å. There are four inequivalent Ge+3.50+ sites. In the first Ge+3.50+ site, Ge+3.50+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing GeSe4 tetrahedra. There are a spread of Ge–Se bond distances ranging from 2.38–2.47 Å. In the second Ge+3.50+ site, Ge+3.50+ is bonded to four Se2- atoms to form corner-sharing GeSe4 tetrahedra. There are a spread of Ge–Se bond distances ranging from 2.35–2.47 Å. In the third Ge+3.50+ site, Ge+3.50+ is bonded to four Se2- atoms to form a mixture of corner and edge-sharing GeSe4 tetrahedra. There are a spread of Ge–Se bond distances ranging from 2.40–2.46 Å. In the fourth Ge+3.50+ site, Ge+3.50+ is bonded to four Se2- atoms to form corner-sharing GeSe4 tetrahedra. There are two shorter (2.63 Å) and two longer (2.64 Å) Ge–Se bond lengths. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 2-coordinate geometry to one K1+ and two Ge+3.50+ atoms. In the second Se2- site, Se2- is bonded in a 2-coordinate geometry to two K1+ and two Ge+3.50+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two K1+ and two Ge+3.50+ atoms. In the fourth Se2- site, Se2- is bonded in a 3-coordinate geometry to three K1+ and two Ge+3.50+ atoms. In the fifth Se2- site, Se2- is bonded in a distorted trigonal non-coplanar geometry to one K1+ and two Ge+3.50+ atoms. In the sixth Se2- site, Se2- is bonded in a 3-coordinate geometry to one K1+ and two Ge+3.50+ atoms. In the seventh Se2- site, Se2- is bonded in a 2-coordinate geometry to three equivalent K1+ and two Ge+3.50+ atoms. In the eighth Se2- site, Se2- is bonded in a 2-coordinate geometry to one K1+ and two Ge+3.50+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRS1987

Mass spectroscopic characterization of the GeSe:GeI4 vapor transport system

The GeSe:GeI4 vapor crystal growth system was characterized mass spectroscopically. A steady-state Knudsen effusion technique was developed to simulate the equilibrium conditions at one end of a vapor transport ampoule. It was found that the previously neglected equilibrium GeSe2(s) = GeSe(v) + 1/2Se2(v) reduces the Se2(v) concentration to an extent that sublimation/condensation of GeSe becomes the dominant transport mechanism. At total pressures near 1 atm the concentration of an additional Ge-Se-I vapor species becomes comparable to that of GeSe(v).

Buchan, Nicholas I.↗
NASA NTRS1988

On the mass transport properties of the GeSe-GeI4 system under normal and reduced gravity conditions

Previous work on the mass transport rate of the GeSe-GeI4 system has been reevaluated using the mass spectrometric results of Buchan and Rosenberger (1987), and considering the presence of GeSe(s) and GeSe2(s) phases in the source material. The present transport rate study confirms the previously derived dominance of the sublimation of GeSe at lower pressures of GeI4, and of chemical vapor transport at higher pressures of GeI4. It is noted that experimentally observed flux anomalies are model-independent.

Palosz, Witold↗