First-principles investigations of transition metal dihydrides, TH₂: T = Sc, Ti, V, Y, Zr, Nb; energetics and chemical bonding

Abstract

Self-consistent full-potential linearized augmented-plane-wave (LAPW) band-structure calculations are performed for the fluorite-type dihydrides ScH2, TiH2, VH2, YH2, ZrH2 and NbH2 as well as for the tetragonal low-temperature phases of TiH2 and ZrH2. For all compounds studied which show metallic behaviour, band structures, densities of states, electron densities and the total-energy minima with respect to the lattice parameters are computed. Additionally, the bulk moduli for the cubic phases are given. Good agreement with experimental data is found where they are available. The results obtained confirm previous interpretations of the tetragonal distortion of the cubic unit cell as a Jahn-Teller-type effect and show how the electron densities of the tetragonally distorted phases depend on the splitting of states near the Fermi level. The total-energy curves for TiH2 and ZrH2 as functions of the c/a ratios show two minima each, of which only the ones for c/a<1 have been observed experimentally.

Local bonding structure in mechanically activated TiH2 and TiH2+graphite mixture

“…However, the band structure calculations show [10,11] that Ti 3d density of states (DOS) of tetragonally distorted TiH 2 (for c/a = 0.926 and 1.068) is very similar to that for the cubic compound with CaF 2 structure where H atoms occupy tetrahedral interstices in the fcc metal lattice. The differences are found only in the close vicinity of the Fermi level caused by the splitting of bands in this energy region.…”

“…A significant change is observed in Ti L␣ XES: an additional low-energy subband (B) located at ∼447.8 eV, i.e., about 4.6 eV lower than the most intensive line (A) appeared. According to electronic structure calculations of TiH 2 [10,11], this subband is formed by Ti3d-H1s bonding. Therefore, we ascribe an additional subband B to a hydrogen-induced state of Ti.…”

Reactive sputtering of δ-ZrH2 thin films by high power impulse magnetron sputtering and direct current magnetron sputtering

“…7 . 1 Using firstprinciple calculations of the electronic structures for δ-ZrH 2 and ε-ZrH 2 , the electrical and mechanical properties have been assessed [6][7][8][9] . The calculated density of state at the Fermi level reported in these studies support experimental results on good electrical conductivity for both phases and the calculations show that the d-bands of zirconium play a dominant role in the electrical transport.…”

Density functional theory studies of the hydrogenation properties of Mg and Ti

“…11 X-ray and neutron-diffraction results by Sidhu et al 12 indicated that H atoms might occupy octahedral sites. A number of theoretical studies with respect to various properties, such as the electronic structure, formation energies, metal-hydrogen and hydrogen-hydrogen interactions, surface properties have been carried out on Mg based [13][14][15] and Ti based [16][17][18][19] hydrogen storage materials as well.…”