Raman, FTIR, Photoacoustic-Infrared, and Inelastic Neutron Scattering Spectra of Ternary Metal Hydride Salts A2MH5, (A = Ca, Sr, Eu; M = Ir, Rh) and Their Deuterides

The vibrational spectra of the ternary metal hydride (deuteride) salts, A2MH5 and A2MD5, where A = calcium, strontium and europium and M = iridium(I) and rhodium(I), have been assigned using Raman, Fourier transform infrared, photoacoustic infrared, and inelastic neutron scattering spectroscopies and density functional theory (DFT) calculations. The wavenumbers of the infrared-active stretching vibrations depend upon the ionization energies of the central metal atom and the cation. The phase transition in calcium pentahydridoiridate(I) was studied as a function of temperature and pressure.