Infrared Spectroscopic and Computational Studies on Li₄FeH₆ with High Gravimetric Hydrogen Density

Abstract

We report the vibrational properties of Li₄FeH₆ with the highest gravimetric hydrogen density in Fe-based complex hydrides. The Fourier transform infrared (FTIR) spectrum shows a broad and weak peak at 600–1000 cm⁻¹ and an intense one at 1400–1800 cm⁻¹, which are assigned with the aid of first-principles calculations to be the H–Fe–H bending modes, and the antisymmetric Fe–H stretching modes, respectively. From the obtained peak frequency of asymmetric stretching modes of Li₄FeH₆, the Fe–H bond length is estimated to be 1.6 Å, which is in good agreement with the one predicted by first-principles calculations.