Mechanical Properties of Formamidinium Halide Perovskites FABX3 (FA=CH(NH2)2;B=Pb, Sn;X=Br, I) by First-Principles Calculations
Abstract: The mechanical properties of formamidinium halide perovskites FABX3 (FA=CH(NH2)2;B=Pb,Sn;X=Br,I) are systematically investigated using first-principles calculations.Our results reveal that FABX3 perovskites possess excellent mechanical flexibility,ductility and strong anisotropy.We shows that the planar organic cation FA+ has an important effect on the mechanical properties of FABX3 perovskites.In addition,our results indicate that (i) the moduli (bulk modulus B,Young's modulus E,and shear modulus G) of FABBr3 are larger than those of FABI3 for the same B atom,and (ii) the moduli of FAPbX3 are larger than those of FASnX3 for the same halide atom.The reason for the two trends is demonstrated by carefully analyzing the bond strength between B and X atoms based on the projected crystal orbital Hamilton population method.