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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Fe7C3 by Materials Project

Fe7C3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. there are three inequivalent Fe sites. In the first Fe site, Fe is bonded in a distorted L-shaped geometry to two equivalent C atoms. Both Fe–C bond lengths are 2.04 Å. In the second Fe site, Fe is bonded in a 3-coordinate geometry to three equivalent C atoms. There is one shorter (1.93 Å) and two longer (2.00 Å) Fe–C bond length. In the third Fe site, Fe is bonded in a 3-coordinate geometry to three equivalent C atoms. All Fe–C bond lengths are 1.98 Å. C is bonded in a 6-coordinate geometry to six Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Fe7C3 by Materials Project

Fe7C3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are five inequivalent Fe sites. In the first Fe site, Fe is bonded in a 3-coordinate geometry to three C atoms. There are a spread of Fe–C bond distances ranging from 1.97–2.04 Å. In the second Fe site, Fe is bonded in a 3-coordinate geometry to three C atoms. There is one shorter (1.93 Å) and two longer (1.98 Å) Fe–C bond length. In the third Fe site, Fe is bonded in a water-like geometry to two equivalent C atoms. Both Fe–C bond lengths are 1.98 Å. In the fourth Fe site, Fe is bonded in a distorted trigonal planar geometry to three C atoms. There is one shorter (1.96 Å) and two longer (1.99 Å) Fe–C bond length. In the fifth Fe site, Fe is bonded in a 4-coordinate geometry to four C atoms. There are a spread of Fe–C bond distances ranging from 2.02–2.44 Å. There are two inequivalent C sites. In the first C site, C is bonded in a 7-coordinate geometry to seven Fe atoms. In the second C site, C is bonded in a 6-coordinate geometry to eight Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

The iron spin transition of deep nitrogen-bearing mineral Fe3N1.2 at high pressure

Abstract Nitrogen is an essential element for life, one of the most abundant volatiles in the atmosphere, and an important component in the Earth’s interior, where iron nitride is an essential host of deep nitrogen. Here, we investigate the pressure-induced electronic spin-pairing transition of iron in siderazot (Fe3N1.2) at pressures up to 45.8 GPa at room temperature, using diamond-anvil cell techniques coupled with synchrotron X-ray emission spectroscopy. The integrated intensity of the satellite emission peak (K′β) decreases upon compression but remains unchanged at pressures greater than 30.5 GPa. In other words, the high-spin to low-spin transition of iron in Fe3N1.2 starts immediately at very low pressures and completes at ~30.5 GPa. The iron spin transition completion pressures increase with the nitrogen concentration of hexagonal close-packed iron nitrides (i.e., Fe3N1.2, Fe7N3, and Fe2N). Moreover, the identity and concentration of light elements in binary iron-rich compounds such as Fe3N, Fe3C, Fe3P, Fe3S, Fe7C3, and Fe7N3, together with their crystal structure, could affect the iron spin transition pressures. The spin transition of iron-rich alloys could alter the bonding nature and the physical properties, including the thermal and electrical conductivity, thereby influencing the thermal state and evolution of planetary interiors.

Geochemistry & Geophysics↗
NASA NTRS2000

Laser pyrolysis fabrication of ferromagnetic gamma'-Fe4N and FeC nanoparticles

Using the laser pyrolysis method, single phase gamma'-Fe4N nanoparticles were prepared by a two step method involving preparation of nanoscale iron oxide and a subsequent gas-solid nitridation reaction. Single phase Fe3C and Fe7C3 could be prepared by laser pyrolysis from Fe(CO)5 and 3C2H4 directly. Characterization techniques such as XRD, TEM and vibrating sample magnetometer were used to measure phase structure, particle size and magnetic properties of these nanoscale nitride and carbide particles. c2000 American Journal of Physics.

NASA Discipline Life Sciences Technologies↗