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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Pressure-induced transformation of Nb 2 O 5 under shock compression from first principles

Ab initio molecular dynamics (AIMD) simulations were carried out to investigate the equation of state of Nb 2 O 5 and its pressure-density relationship under shock conditions. Here, the focus of this study is on the monoclinic B-Nb 2 O 5 (C2/c) polymorph. Enthalpy calculations from AIMD trajectories at 300 K show that the pressure-induced transformation between the thermody-namically most stable crystalline monoclinic parent phase H-Nb 2 O 5 (P2/m) and B-Nb 2 O 5 occurs at ~1.9 GPa. This H→B transition is energetically more favorable than the H→L(Pmm2) pressure-induced transition recently observed at ~5.9-9.0 GPa. The predicted shock properties of Nb 2 O 5 polymorphs are also compared to their Nb and NbO 2 counterparts to assess the impact of niobium oxidation on shock response.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Nb3B4 by Materials Project

Nb3B4 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded to twelve B+1.50- atoms to form a mixture of edge and face-sharing NbB12 cuboctahedra. There are eight shorter (2.47 Å) and four longer (2.51 Å) Nb–B bond lengths. In the second Nb2+ site, Nb2+ is bonded in a 7-coordinate geometry to seven B+1.50- atoms. There are a spread of Nb–B bond distances ranging from 2.39–2.59 Å. There are two inequivalent B+1.50- sites. In the first B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to seven Nb2+ and two equivalent B+1.50- atoms. Both B–B bond lengths are 1.85 Å. In the second B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to six Nb2+ and three B+1.50- atoms. The B–B bond length is 1.82 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3B2 by Materials Project

Nb3B2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Nb2+ sites. In the first Nb2+ site, Nb2+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All Nb–B bond lengths are 2.55 Å. In the second Nb2+ site, Nb2+ is bonded in a hexagonal planar geometry to six equivalent B3- atoms. There are four shorter (2.47 Å) and two longer (2.52 Å) Nb–B bond lengths. B3- is bonded in a 9-coordinate geometry to eight Nb2+ and one B3- atom. The B–B bond length is 1.86 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbB by Materials Project

NbB crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Nb3+ is bonded in a 7-coordinate geometry to seven equivalent B3- atoms. There are a spread of Nb–B bond distances ranging from 2.42–2.60 Å. B3- is bonded in a 9-coordinate geometry to seven equivalent Nb3+ and two equivalent B3- atoms. Both B–B bond lengths are 1.89 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NbB2 by Materials Project

NbB2 is hexagonal omega structure structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. Nb is bonded to twelve equivalent B atoms to form a mixture of face and edge-sharing NbB12 cuboctahedra. All Nb–B bond lengths are 2.45 Å. B is bonded in a 9-coordinate geometry to six equivalent Nb and three equivalent B atoms. All B–B bond lengths are 1.80 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb5B6 by Materials Project

Nb5B6 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are three inequivalent Nb+2.40+ sites. In the first Nb+2.40+ site, Nb+2.40+ is bonded to twelve B2- atoms to form a mixture of edge and face-sharing NbB12 cuboctahedra. There are eight shorter (2.47 Å) and four longer (2.50 Å) Nb–B bond lengths. In the second Nb+2.40+ site, Nb+2.40+ is bonded in a 7-coordinate geometry to seven B2- atoms. There are a spread of Nb–B bond distances ranging from 2.38–2.60 Å. In the third Nb+2.40+ site, Nb+2.40+ is bonded in a 7-coordinate geometry to seven B2- atoms. There are a spread of Nb–B bond distances ranging from 2.42–2.59 Å. There are three inequivalent B2- sites. In the first B2- site, B2- is bonded in a 9-coordinate geometry to seven Nb+2.40+ and two equivalent B2- atoms. Both B–B bond lengths are 1.85 Å. In the second B2- site, B2- is bonded in a 9-coordinate geometry to seven Nb+2.40+ and two equivalent B2- atoms. Both B–B bond lengths are 1.88 Å. In the third B2- site, B2- is bonded in a 9-coordinate geometry to six Nb+2.40+ and three B2- atoms. The B–B bond length is 1.82 Å.

36 MATERIALS SCIENCE↗