 First Principles Calculations Investigate the Crystal Structures, Elastic and Anisotropic Properties of CH3NH3BX3B equals SN, PB, X equals BR, I, Compounds as Solar Cell Absorber Layers. The type and strength of chemical bond BX determine the elastic properties, and the interaction among organic and inorganic ions has negligible effect for elastic properties. The perovskites have good ductal ability due to low shear modulus and strong anisotropy derived from elastic constants, chemical bonds, and symmetry. This article was authored by Jingfeng.