Raman and infrared spectroscopic studies on Li4RuH6combined with first-principles calculations

Abstract

We have studied the vibrational properties of Li4RuH6, consisting of the lightest Li+metal cation, and the octahedral [RuH6]4-complex anion by Raman and Fourier Transform Infrared (FTIR) spectroscopies and first-principles calculations. The Li+forms a cubic framework with the [RuH6]4-inside as the local atomic arrangement of Li4RuH6, which is similar to that of a related M′2RuH6with a divalent metal cation MB (MB = Mg, Ca, Sr, Ba, and Yb). Comparing the vibrational studies on Li4RuH6with M′2RuH6, the peak frequencies for the antisymmetric RuH stretching mode (Vanti-str) showed a reasonable relationship with the Ru-H bond distances (dRu-H) in [RuH6]4-, with higher peak frequencies for shorter bond distances according to the linear relation Vanti-str = 10052 - 4990 × (dRu-H).