First-Principles Study on the Structural and Magnetic Properties of Iron Hydride

Abstract

The magnetic and structural properties of iron hydride FeH with the double hexagonal close-packed (dhcp) and hexagonal close-packed (hcp) structures are investigated by first-principles density-functional theory calculations with a spin-polarized form of generalized gradient approximation. All the calculations are performed using all-electron fullpotential linearized augmented plane wave method. Both dhcp and hcp FeH are ferromagnetic at ambient pressure. The ferromagnetic ordering of the dhcp structure collapses at a pressure of 48 GPa, while that of the hcp structure vanishes gradually from 48 GPa. The modification in the density of states (DOS) due to the applied pressure causes the collapse of the magnetization. The difference in magnetic moment reduction between dhcp and hcp FeH is attributed to their DOS around the Fermi level. The calculated magnetocrystalline anisotropy energies between in-plane and out-of-plane spin orientations are found to be 124 eV/Fe for the dhcp structure, and 100 eV/Fe for the hcp structure. The easy axis is in-plane direction for both structures.

High‐Pressure Geophysical Properties of Fcc Phase FeHX

“…Spectra at both pressures have similar (isomer) central shifts (CS) with respect to α‐iron at comparable pressure, are in reasonable agreement with the CS previously reported by Narygina et al () at 47 GPa, and are distinct from the central shift reported for either the dhcp or hcp phases (supporting information Table S2). In agreement with previous studies, the fcc phase of FeH X is not ferromagnetic, in contrast to that of the dhcp and hcp phases (Narygina et al, ; Tsumuraya et al, ), and as such SMS functions as a secondary confirmation of the structure of our samples, as there is no evidence of magnetic hyperfine field splitting in the measured spectra.…”

Electronic and magnetic properties of iron hydride under pressure: An experimental and computational study using x-ray absorption spectroscopy and x-ray magnetic circular dichroism at the Fe K edge

“…The symmetry of one of these sites Neutron powder diffraction experiments performed on quenched FeD samples [25] showed that D atoms were positioned slightly off the center of the interlayer at z H = 0.882. This vertical displacement was confirmed for FeH by DFT calculations [26]. In the present study we first performed an energy minimization by relaxing the atomic positions of H atoms and found z H = 0.880, in good agreement with both experiment and previous calculations.…”

The Search for Superconductivity in High Pressure Hydrides

“…359 DFT calculations predicted that metallic R3m and Im3m symmetry H 3 S phases became preferred above 111 and 180 GPa, respectively. The EPC of both structures was found to be particularly high, and the T c was estimated as being [155][156][157][158][159][160][161][162][163][164][165][166] GPa. The cubic Im3m structure is illustrated in Fig.…”

“…The FM to NM transition of the hcp and dhcp phases of FeH under pressure have been studied via DFT calculations. 159 Recently, the FeH 5 phase illustrated in Fig. 7(d) was synthesized after laser heating in a DAC above 130 GPa.…”