  CaOFeS is a semiconducting oxysulfide with polar layered triangular
structure. Here a comprehensive theoretical study has been performed to reveal
its physical properties, including magnetism, electronic structure, phase
transition, magnetodielectric effect, as well as optical absorption. Our
calculations confirm the Ising-like G-type antiferromagnetic ground state
driven by the next-nearest neighbor exchanges, which breaks the trigonal
symmetry and is responsible for the magnetodielectric effect driven by exchange
striction. In addition, a large coefficient of visible light absorption is
predicted, which leads to promising photovoltaic effect with the maximum
light-to-electricity energy conversion efficiency up to 24.2%.
