First-principles study of the pressure dependence of the structural and vibrational properties of the ternary metal hydride Ca2RuH6

The influence of pressure on the structural and vibrational properties of Ca2RuH6 has been investigated using periodic density functional theory calculations performed at the local density approximation (LDA) and generalized gradient approximation (GGA) levels. At ambient pressure, the calculated structure and vibrational frequencies are in satisfactory agreement with experimental data. The calculated P-V curves could be fitted with the Vinet equation of state, yielding B0=67.6 and B0=58.5 GPa at the LDA and GGA levels, respectively, and B=4.0 at both theoretical levels. The unit cell parameter is found to decrease faster with increasing pressure than the Ru–H bond length. The calculated pressure dependence of the vibrational frequencies agrees well with experiment for 5(T2g) but not for 9(A1g)