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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Nb3Si by Materials Project

Nb3Si is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Nb is bonded to eight equivalent Nb and four equivalent Si atoms to form NbNb8Si4 cuboctahedra that share corners with twelve equivalent NbNb8Si4 cuboctahedra, edges with eight equivalent SiNb12 cuboctahedra, edges with sixteen equivalent NbNb8Si4 cuboctahedra, faces with four equivalent SiNb12 cuboctahedra, and faces with fourteen equivalent NbNb8Si4 cuboctahedra. All Nb–Nb bond lengths are 2.89 Å. All Nb–Si bond lengths are 2.89 Å. Si is bonded to twelve equivalent Nb atoms to form SiNb12 cuboctahedra that share corners with twelve equivalent SiNb12 cuboctahedra, edges with twenty-four equivalent NbNb8Si4 cuboctahedra, faces with six equivalent SiNb12 cuboctahedra, and faces with twelve equivalent NbNb8Si4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Si by Materials Project

Nb3Si crystallizes in the cubic Pm-3n space group. The structure is three-dimensional. Nb is bonded in a 6-coordinate geometry to two equivalent Nb and four equivalent Si atoms. Both Nb–Nb bond lengths are 2.56 Å. All Nb–Si bond lengths are 2.87 Å. Si is bonded to twelve equivalent Nb atoms to form a mixture of face and edge-sharing SiNb12 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Si by Materials Project

Nb3Si crystallizes in the tetragonal P4_2/n space group. The structure is three-dimensional. there are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 2-coordinate geometry to two equivalent Si atoms. There are one shorter (2.62 Å) and one longer (2.66 Å) Nb–Si bond lengths. In the second Nb site, Nb is bonded in a 4-coordinate geometry to four equivalent Si atoms. There are a spread of Nb–Si bond distances ranging from 2.60–2.72 Å. In the third Nb site, Nb is bonded in a 2-coordinate geometry to three equivalent Si atoms. There are a spread of Nb–Si bond distances ranging from 2.59–2.87 Å. Si is bonded in a 9-coordinate geometry to nine Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Nb3Si by Materials Project

Nb3Si crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are two inequivalent Nb sites. In the first Nb site, Nb is bonded in a distorted L-shaped geometry to two equivalent Nb and two equivalent Si atoms. Both Nb–Nb bond lengths are 2.90 Å. Both Nb–Si bond lengths are 2.60 Å. In the second Nb site, Nb is bonded in a distorted body-centered cubic geometry to eight Nb atoms. All Nb–Nb bond lengths are 2.91 Å. Si is bonded in a distorted square co-planar geometry to four equivalent Nb atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Data Science Enabled Enabled Discovery of Superconductors (Final Progress Report)

This Final Technical Report describes efforts by 4 PIs at the University of Florida (Peter Hirschfeld, Richard Hennig, Greg Stewart and James Hamlin), over the period September 2019-August 2023, to use data science and machine learning techniques to discover new conventional superconductors. The PIs constructed a discovery loop with two theorists and two experimentalists to: develop algorithms to machine learn descriptors correlating strongly with the critical temperature Tc (PI's Peter Hirschfeld, UF Physics and Richard Hennig, UF Materials Science and En), synthesize and measure properties of promising materials, and feed back the knowledge gained into the prediction algorithm. This work was motivated by the theoretical prediction and experimental discovery of high-pressure, high-pressure hydride superconductors, and to find ways to recreate the high critical temperatures in these systems at ambient pressure. Highlights from the grant include: 1) a new equation for Tc in terms of moments of the electron-phonon spectral function, improving on the so-called Allen-Dynes equation (1975); 2) study of the metastable A15 superconductor Nb3Si, formed under explosive compression at ~1000GPa to determine the kinetic barrier to the ground state structure; 3) the development of ultra-fast machine-learned atomic potentials for molecular dynamics, and 4) the discovery of superconductivity at 19K in WB2 arising from metastable defect structures in the crystal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗