First-principles study of the pressure dependence of the structural and vibrational properties of the ternary metal hydride Ca_2RuH_6

摘要

The influence of pressure on the structural and vibrational properties of Ca_2RuH_6 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 B_0=67.6 and B_0=58.5 GPa at the LDA and GGA levels, respectively, and B'_0=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 v_5(T_(2g)) but not for v_9(A_(1g)).