DFT study of the CaNi5Hx compounds (0.0 ⩽ x ⩽ 1.0)

Density functional theory based electronic structure calculations which included crystal structure optimizations were performed for CaNi5Hx (x = 0.0, 0.25, 0.5, 1.0) compounds. Only hydrides with one H atom per unit cell were considered in the present work. Site preference of hydrogen atoms and energetics of hydride formation were investigated. It was found that hydrogen atoms prefer, in notation of space group P6/mmm, 12n sites and that 3f sites are the second most preferred sites what is compatible with previous neutron diffraction studies. Enthalpy of formation of α solid solution and for α → β reaction were calculated and compared with available experimental data and fair agreement was found between calculated and experimental values of enthalpies of formation.