Structure and vibrational spectra of formamidinium bromide

Abstract

Crystal structure, electron states and vibrational spectra of formamidinium (FA) bromide crystal are studied with the use of the quantum-mechanical density functional computational methods. The obtained results show good agreement when compared with available experimental data. It is shown that cation-anion binding is purely ionic. The bottom state of conduction band corresponds to the LUMO state of the FA cation. The upper state of valence band corresponds to the 4p lone-pair of the Br anion. Particular attention is paid to N-H...Br hydrogen bonds, for which the characteristic spectroscopic features are determined. The obtained results can be useful in studying the FA-based perovskite compounds promising for the photovoltaic applications