Quantum state of hydrogen inLaNi5

Abstract

The quantum state of the hydrogen atom that is trapped at the most stable octahedral interstitial site in the LaNi 5 crystal is determined. A three-dimensional potential-energy surface for the hydrogen atom around the 3f site is obtained by applying first-principles electronic-structure calculations. The time-independent Schrödinger equation for the hydrogen atom under the potential obtained is solved. The hydrogen wave function distributes over the neighboring sites, 6i-3f-6i, that have been proposed by various workers so far. The energy spectra of the hydrogen atom well explain those of inelastic neutron scattering.

Hydrogen quantum effects in hydride LaNi5H7

“…2(a), the potential energy surface has a potential minimum point at the classical hydrogen position, while the potential energy surface at the 6i site for the solid solution phase has two minimum potential points. 3,4 In this case, the potential energy surface has a step structure in the Z direction as explained latter (see Fig. 3), and its step height is 0.25 eV, which is comparable to the zero point energy of the hydrogen atom.…”

“…These are powerful tools for exploring the quantum effects of light nuclei on neutron scatterings from dilute hydrogen in a solid solution of LaNi 5 H 0:5 . 3 We also showed that some zero point vibrational effects are present at all hydrogen sites in the solid solution phase of LaNi 5 H. 4 Some sites are combined into one site due to the zero point vibration. In this study, we reveal the hydrogenatom quantum effects in the hydride, and we clarify their role.…”

“…3. To construct the Hamiltonian matrix, we used two different complete orthonormal basis sets to treat the boundary conditions.…”

Analyses of hydrogen local environments in metals and intermetallic compounds using inelastic neutron scattering calculations based on first-principles hydrogen adiabatic potentials

“…The hydrogen nuclear wavefunctions were calculated by solving the Schrödinger equation under the theoretical adiabatic potential [10][11][12][13][14]. Sugimoto and Fukai [11] calculated hydrogen nuclear wave functions using an empirical interatomic potential.…”

“…The potential in the reciprocal space was obtained from the Fourier transformation of the total energies of the crystals whose unit cells contained a hydrogen atom at several positions on the high-symmetry paths. Kaneko et al [14] calculated the hydrogen nuclear wavefunctions and the INS peak energies for a more complicated material, a hydrogen primary solid solution of LaNi 5 , and calculated the adiabatic potential through first-principles band calculations of a model structure of the solid solution with the hydrogen atom placed on mesh grids in a box centered at a hydrogen interstitial site. However, more than one primary peak in each experimental INS collected with the momentum transfer vector perpendicular and parallel to the c-axis of the hexagonal crystal [7] was unassigned by the calculated hydrogen nuclear states of the primary hydrogen interstitial site.…”