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14 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ti(FeSe2)2 by Materials Project

Ti(FeSe2)2 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one Ti(FeSe2)2 sheet oriented in the (0, 0, 1) direction. Ti4+ is bonded to six Se2- atoms to form distorted TiSe6 octahedra that share corners with two equivalent FeSe5 trigonal bipyramids, edges with two equivalent TiSe6 octahedra, and faces with four equivalent FeSe5 trigonal bipyramids. There are a spread of Ti–Se bond distances ranging from 2.57–2.84 Å. Fe2+ is bonded to five Se2- atoms to form FeSe5 trigonal bipyramids that share a cornercorner with one TiSe6 octahedra, corners with two equivalent FeSe5 trigonal bipyramids, edges with three equivalent FeSe5 trigonal bipyramids, and faces with two equivalent TiSe6 octahedra. The corner-sharing octahedral tilt angles are 73°. There are a spread of Fe–Se bond distances ranging from 2.32–2.54 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to one Ti4+ and three equivalent Fe2+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Ti4+ and two equivalent Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na3(FeSe2)2 by Materials Project

Na3(FeSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with eight equivalent FeSe4 tetrahedra, edges with two equivalent FeSe4 tetrahedra, and faces with two equivalent NaSe6 octahedra. There are a spread of Na–Se bond distances ranging from 2.94–3.11 Å. In the second Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.95–3.56 Å. Fe+2.50+ is bonded to four Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent NaSe6 octahedra, an edgeedge with one NaSe6 octahedra, and edges with two equivalent FeSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 14–63°. There are a spread of Fe–Se bond distances ranging from 2.39–2.42 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to four Na1+ and two equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent Na1+ and two equivalent Fe+2.50+ atoms. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to five Na1+ and two equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb3(FeSe2)2 by Materials Project

Rb3(FeSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Rb1+ sites. In the first Rb1+ site, Rb1+ is bonded to six Se2- atoms to form RbSe6 octahedra that share corners with eight equivalent FeSe4 tetrahedra, edges with two equivalent FeSe4 tetrahedra, and faces with two equivalent RbSe6 octahedra. There are a spread of Rb–Se bond distances ranging from 3.39–3.54 Å. In the second Rb1+ site, Rb1+ is bonded in a 7-coordinate geometry to seven Se2- atoms. There are a spread of Rb–Se bond distances ranging from 3.39–4.02 Å. Fe+2.50+ is bonded to four Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent RbSe6 octahedra, an edgeedge with one RbSe6 octahedra, and edges with two equivalent FeSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–63°. There are a spread of Fe–Se bond distances ranging from 2.40–2.47 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent Rb1+ and two equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 8-coordinate geometry to six Rb1+ and two equivalent Fe+2.50+ atoms. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to five Rb1+ and two equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K3(FeSe2)2 by Materials Project

K3(FeSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to six Se2- atoms to form KSe6 octahedra that share corners with eight equivalent FeSe4 tetrahedra, edges with two equivalent FeSe4 tetrahedra, and faces with two equivalent KSe6 octahedra. There are a spread of K–Se bond distances ranging from 3.26–3.41 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 3.26–3.95 Å. Fe+2.50+ is bonded to four Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent KSe6 octahedra, an edgeedge with one KSe6 octahedra, and edges with two equivalent FeSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–62°. There are a spread of Fe–Se bond distances ranging from 2.40–2.46 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent K1+ and two equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 7-coordinate geometry to five K1+ and two equivalent Fe+2.50+ atoms. In the third Se2- site, Se2- is bonded in a 6-coordinate geometry to six K1+ and two equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(FeSe2)2 by Materials Project

Cr(FeSe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Cr3+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with twelve equivalent FeSe6 octahedra, edges with two equivalent CrSe6 octahedra, and faces with two equivalent FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 53–56°. There are two shorter (2.53 Å) and four longer (2.56 Å) Cr–Se bond lengths. Fe+2.50+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent CrSe6 octahedra, edges with six equivalent FeSe6 octahedra, and a faceface with one CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 53–56°. There are a spread of Fe–Se bond distances ranging from 2.40–2.67 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Cr3+ and three equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to one Cr3+ and three equivalent Fe+2.50+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeSe2 by Materials Project

FeSe2 is Marcasite structured and crystallizes in the orthorhombic Pnnm space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent Se+1.50- atoms to form a mixture of corner and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles are 57°. There are two shorter (2.37 Å) and four longer (2.38 Å) Fe–Se bond lengths. Se+1.50- is bonded in a 3-coordinate geometry to three equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Cr(FeSe2)2 by Materials Project

Cr(FeSe2)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. Cr3+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Cr–Se bond distances ranging from 2.45–2.51 Å. There are two inequivalent Fe+2.50+ sites. In the first Fe+2.50+ site, Fe+2.50+ is bonded in a distorted pentagonal planar geometry to five Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.36–2.50 Å. In the second Fe+2.50+ site, Fe+2.50+ is bonded in a distorted pentagonal planar geometry to five Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.35–2.57 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to one Cr3+ and two Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded to one Cr3+ and three Fe+2.50+ atoms to form a mixture of distorted edge and corner-sharing SeCrFe3 tetrahedra. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to one Cr3+ and two Fe+2.50+ atoms. In the fourth Se2- site, Se2- is bonded to one Cr3+ and three Fe+2.50+ atoms to form a mixture of distorted edge and corner-sharing SeCrFe3 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V(FeSe2)2 by Materials Project

V(FeSe2)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. V2+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of V–Se bond distances ranging from 2.42–2.77 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.41–2.88 Å. In the second Fe3+ site, Fe3+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Fe–Se bond distances ranging from 2.33–2.43 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to one V2+ and three Fe3+ atoms. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent V2+ and two Fe3+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to one V2+ and three Fe3+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent V2+ and two Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V(FeSe2)2 by Materials Project

V(FeSe2)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. V2+ is bonded to six Se2- atoms to form distorted VSe6 octahedra that share corners with six equivalent FeSe6 octahedra, edges with two equivalent VSe6 octahedra, edges with four equivalent FeSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 52–57°. There are a spread of V–Se bond distances ranging from 2.39–2.75 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent VSe6 octahedra, corners with six equivalent FeSe6 octahedra, edges with two equivalent FeSe6 octahedra, a faceface with one VSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 51–57°. There are a spread of Fe–Se bond distances ranging from 2.43–2.53 Å. In the second Fe3+ site, Fe3+ is bonded to six Se2- atoms to form distorted FeSe6 octahedra that share corners with six equivalent FeSe6 octahedra, edges with two equivalent FeSe6 octahedra, edges with four equivalent VSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Fe–Se bond distances ranging from 2.38–2.70 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to one V2+ and four Fe3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent V2+ and three Fe3+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent V2+ and two Fe3+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to one V2+ and three Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ti(FeSe2)2 by Materials Project

Ti(FeSe2)2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. Ti4+ is bonded to six Se2- atoms to form distorted TiSe6 octahedra that share corners with six equivalent FeSe6 octahedra, edges with two equivalent TiSe6 octahedra, edges with four equivalent FeSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 53–58°. There are a spread of Ti–Se bond distances ranging from 2.44–2.74 Å. There are two inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent TiSe6 octahedra, corners with six equivalent FeSe6 octahedra, edges with two equivalent FeSe6 octahedra, a faceface with one TiSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 49–58°. There are a spread of Fe–Se bond distances ranging from 2.44–2.58 Å. In the second Fe2+ site, Fe2+ is bonded to six Se2- atoms to form FeSe6 octahedra that share corners with six equivalent FeSe6 octahedra, edges with two equivalent FeSe6 octahedra, edges with four equivalent TiSe6 octahedra, and a faceface with one FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Fe–Se bond distances ranging from 2.41–2.59 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Ti4+ and three Fe2+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to one Ti4+ and four Fe2+ atoms. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Ti4+ and two Fe2+ atoms. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to one Ti4+ and three Fe2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on FeSe2 by Materials Project

FeSe2 is pyrite-like structured and crystallizes in the cubic Pa-3 space group. The structure is three-dimensional. Fe3+ is bonded to six equivalent Se+1.50- atoms to form corner-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles are 63°. All Fe–Se bond lengths are 2.40 Å. Se+1.50- is bonded in a distorted trigonal planar geometry to three equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V(FeSe2)2 by Materials Project

V(FeSe2)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. V2+ is bonded to six Se2- atoms to form VSe6 octahedra that share corners with twelve equivalent FeSe6 octahedra, edges with two equivalent VSe6 octahedra, and faces with two equivalent FeSe6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are two shorter (2.53 Å) and four longer (2.54 Å) V–Se bond lengths. Fe3+ is bonded to six Se2- atoms to form distorted FeSe6 octahedra that share corners with six equivalent VSe6 octahedra, edges with six equivalent FeSe6 octahedra, and a faceface with one VSe6 octahedra. The corner-sharing octahedra tilt angles range from 51–56°. There are a spread of Fe–Se bond distances ranging from 2.41–2.79 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to one V2+ and three equivalent Fe3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent V2+ and three equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(FeSe2)2 by Materials Project

BaFe2Se4 crystallizes in the tetragonal I4/m space group. The structure is three-dimensional. Ba2+ is bonded to twelve equivalent Se2- atoms to form BaSe12 cuboctahedra that share corners with eight equivalent FeSe4 tetrahedra, edges with eight equivalent BaSe12 cuboctahedra, edges with eight equivalent FeSe4 tetrahedra, and faces with two equivalent BaSe12 cuboctahedra. There are four shorter (3.41 Å) and eight longer (3.69 Å) Ba–Se bond lengths. Fe3+ is bonded to four equivalent Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent BaSe12 cuboctahedra, edges with four equivalent BaSe12 cuboctahedra, and edges with two equivalent FeSe4 tetrahedra. All Fe–Se bond lengths are 2.27 Å. Se2- is bonded in a 5-coordinate geometry to three equivalent Ba2+ and two equivalent Fe3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Targeted synthesis of predicted metastable compounds using modulated elemental reactants

Three metastable compounds predicted to be kinetically stable using an “island” approach were successfully synthesized from designed modulated elemental reactants. Fe0.8V0.2Se2 was synthesized by depositing ultrathin elemental layers in a V|Fe|Se sequence to control the local composition. An alloyed rock salt structured Pb3Mn2Se5 constituent layer, which does not exist as a bulk compound, was synthesized in the heterostructure (Pb3Mn2Se5)0.6VSe2 by depositing a precursor with a V|Se|Pb|Se|Mn|Se|Pb|Se|Mn|Se|Pb|Se sequence of elemental layers that mimicked the compositional profile of the targeted heterostructure. The heterostructure (PbSe)1+δ(FeSe2)2 was prepared by depositing a precursor with a repeating layering sequence of Fe|Pb|Fe|Se, where each sequence contains the number of atoms required to form a single unit cell. In all three systems, the local compositions in the layer sequence kinetically favored the nucleation and growth of the targeted products during the deposition. The diffusion lengths to form the targeted compounds were short, and the diffusion was limited by postdeposition low temperature annealing to favor the growth of the targeted compounds and avoid the decomposition into a mixture of thermodynamically stable compounds.

Lemon, Mellie (ORCID:0000000328705881)↗