First-Principles Calculations to Investigate the Mechanical Structure and Optical Properties of Lead Halide Perovskite CH3NH3PbI3
Truphena J. Kipkwarkwar, Philip Nyawere, Christopher M. Maghanga
Abstract
We report the study of the mechanical structure and optical properties of lead halide perovskite CH3NH3PbI3 using ab initio methods. The ground state energy calculations were performed within density functional theory and generalized gradient approximation using the pseudopotential method with plane-wave basis sets. The norm conserving pseudopotential was used. The ground state properties of the electronic structure of the perovskite were used and elastic parameters such as bulk modulus B, Young’s modulus E, shear modulus G, and Poisson’s ratio <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mi>υ</a:mi> </a:math> were determined and found to be in good agreement with experimental values. The ratio <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mi>B</c:mi> <c:mo>/</c:mo> <c:mi>G</c:mi> </c:math> obtained was found to be greater than 1.75. Poisson’s ratio ( <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>υ</e:mi> </e:math> ) was obtained as 0.25 implying that CH3NH3PbI3 is a ductile material. The absorption coefficient within the energy range of 0 to 6 eV was found to be 5.76 × 105 cm−1 indicating maximum absorption. The absorption coefficient compares well with the available experimental and computed values.