First principles study of the electronic, elastic and vibrational properties of BiOI

BiOI is reported to be a promising photocatalytic material for splitting water and decomposing pollutants in the visible range. However, previous investigations focus mainly on its photocatalytic property and other properties are not well studied. Here we put our effort to study the electronic, elastic and vibrational properties of BiOI. The results indicate that BiOI is an indirect narrow band gap semiconductor. Bi-O bonds have both covalent and ionic characteristics while Bi-I bonds may have more ionic nature. BiOI is mechanically and dynamically stable. However, calculated directional bulk and Young's moduli reveal that it is seriously mechanically anisotropic, originating from its layered structure. Its infrared absorption spectrum is simulated and four peaks are found. The origins of these peaks are explored based on the calculated Born effective charges and vibrational eigenvectors at the Brillouin zone center. In addition, the dielectric constants of BiOI are computed and discussed. We hope our study will enrich the knowledge of BiOI and other similar materials.