DFT Study of Mechanical Properties and Stability of Cubic Methylammonium Lead Halide Perovskites (CH₃NH₃PbX₃, X = I, Br, Cl)

Abstract

In this study, using the density functional theory, the mechanical properties of methylammonium lead halide perovskites (CH 3 NH 3 PbX 3 , X = I, Br, Cl) were investigated. Young's modulus, bulk modulus, and shear modulus, Poisson's ratio, and many other parameters were calculated using the PBEsol and vdW approximations. Also, in this work, utilizing a new accuracy in calculating the elastic constants, the intense conflict between the previous theoretical results and the experimental data were fixed. Moreover, for the first time, through combination of the PBEsol and vdW methods, the effect of the interaction between methylammonium and PbX 3 scaffold on the mechanical properties of lead halide perovskites was well cleared. In continuation, using the PBEsol+vdW method, a phase transition appeared for the MAPbBr 3 and MAPbCl 3 structures, which proved more stability of MAPbBr 3 and MAPbCl 3 in comparison with MAPbI 3 . In what follows, by studying these materials under an applied strain beyond the harmonic region, the transition zone to the plastic area in the strain region of 5.5% and smaller was identified, and the small values of the aforementioned applied strains were found to be the reason for the instability of these materials at room temperature and above.

Theoretical Progress on the Relationship between the Structures and Properties of Perovskite Solar Cells

“…Computational studies of the tunable properties such as electronic structures under external pressure for MAPbX 3 (X = I, Br, Cl) and all-inorganic halide perovskites CsMX 3 were reported. [91][92][93][94] Using first-principles calculations, Liu et al [95] found that CsPbI 3 under appropriate strain engineering exhibited ferroelectric and topological orders simultaneously, namely a ferroelectric topological insulator. The bulk polarization was stabilized by the metallic topological surface states, because it created an intrinsic shortcircuit condition as innate metallic electrodes, allowing automatic dissipation of surface charges.…”

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

“…Although the PCE of FA‐based PSCs has exponentially increased for several years, the basic working mechanism of PSCs has not been fully clarified. Density functional theory has been extensively used to investigate the electronic structure and other properties of various perovskite materials, with different corrections incorporated to improve agreement with the experimental data . The properties of perovskite materials can also be predicted using software, such as the Vienna Ab Initio Simulation Package and Quantum Espresso, etc.…”

“…Density functional theory has been extensively used to investigate the electronic structure and other properties of various perovskite materials, with different corrections incorporated to improve agreement with the experimental data. [36,[74][75][76][77][78][79][80][81][82][83] The properties of perovskite materials can also be predicted using software, such as the Vienna Ab Initio Simulation Package [74] and Quantum Espresso, [76] etc.…”

Extensive investigation of structural, electronic, optical, and thermoelectric properties of hybrid perovskite ( CH 3 NH 3 PbBr 3 ) with mechanical stability constants

“…Also, by changing the appropriate ex-correlation potential, calculated elastic constants show a 20% to 30% increment compared to elastic constants reported in previous studies. 65 The computed value of the transverse and longitudinal component of sound velocity, the average value of sound velocity and Debye temperature are summarized in Table 4. From Equations (15) to (18), the Debye temperature depends upon bulk modulus, shear modulus, and density of the material.…”

“…Therefore, a difference of 40% to 50% has been observed with the theoretical values of Debye temperature. 43,65 The requirement of these parameters is to study the scattering of charge carrier by phonon in HOIPs.…”