Novel structure of AgInS2 compound under high pressure: First principles calculations

The phase transition of AgInS2 at high pressure has been predicted by means of a newly developed particle swarm optimization (PSO) algorithm for crystal structure prediction. When the pressure exceeds 12.5 GPa, a new phase which belongs to the cubic Fd-3m was found. In the whole Brillouin, no imaginary phonon frequencies zone indicates the phase is dynamically stable at zero pressure. Our calculations with the HSE06 functional yield a narrower band gap (1.2eV) for the high pressure structure than that for the ambient pressure structure. The calculations of optical properties predicate a red shift of the optical spectrum from Fd-3m to I-42d structure of AgInS2 compound.