The Influence of the A Monovalent Cation on Structural and Vibrational Properties of AVF ₃ Perovskites: A DFT Computational Study

Abstract

ABSTRACT The IR and Raman spectra of five AVF 3 compounds (A = Li, Na, K, Rb, and Cs) is computed by using an all electron Gaussian type basis set, the hybrid B3LYP functional, and the CRYSTAL code. For the Cs and Rb compounds, only the cubic ( ) spectra are generated, corresponding to the most stable structure. Also for KVF 3 , NaVF 3 , and LiVF 3 , the cubic spectra are computed, for comparison with the Rb and Cs compounds. The spectra corresponding to a minimum of the total energy along the group‐subgroup chain cubic‐tetragonal ‐orthorhombic(Pnma) are also generated for the three lighter compounds. The role of the A cation varies along the series, as expected from the very large mass and ionic radius differences. The deformation of the VF 6 octahedra becomes very large for the Li and Na compounds, as documented by the spectra of the Pnma phase, which are very different from the cubic ones.