Mechanical Properties of Formamidinium Halide Perovskites FABX3 (FA = CH(NH2)2; B = Pb, Sn; X = Br, I) From First-Principles

TL;DR

This study uses first-principles calculations to analyze the mechanical properties of formamidinium halide perovskites, revealing their flexibility, anisotropy, and how composition influences their elastic moduli.

Contribution

It provides the first detailed computational analysis of the mechanical properties of FABX3 perovskites, highlighting the effects of organic cation and halide composition.

Findings

FABX3 perovskites exhibit excellent mechanical flexibility and ductility.

Moduli of FABBr3 are larger than FABI3 for the same B atom.

Moduli of FAPbX3 are larger than FASnX3 for the same halide.

Abstract

The mechanical properties of formamidinium halide perovskite FABX3(FA = CH(NH2)2; B = Pb, Sn; X = Br, I) were systematically investigated by using the first-principles calculations. Our results reveal that FABX3 perovskites possess excellent mechanical flexibility, ductility and strong anisotropy. It 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 of the two trends was demonstrated by carefully analyzing the bond strength between B and X atom based on the projected crystal orbital Hamilton population method.