Mechanical and thermodynamic properties of CsPbI۳-xBrx(x= ۰.۵, ۱.۵, ۲.۵) compounds: An ab initio investigation

The mechanical, thermodynamic, properties of CsPbI۳-xBrx (x= ۰.۵, ۱.۵, ۲.۵) compounds within GGAapproximations have been studied. The calculations are performed using the QUANTUM-ESPRESSOcomputational package based on the density functional theory (DFT) and the pseudo-potential method.The calculated elasticity parameters illustrated that CsPbI۳-xBrx (x= ۰.۵, ۱.۵, ۲.۵) compounds havemechanical stability conditions at ambient pressure. The calculation of the elastic modulus shows thatwith the increase of Br concentration, the elastic modulus also increases. The calculation of B/G showedthat its value is greater than ۱.۷۵ for all perovskites, which indicates the flexibility of the studiedcompounds. Thermodynamic calculation shows that the increasing entropy relative to temperaturerefers to the endothermic properties of the studied compounds