First-principle analysis of the structural, mechanical, optical and electronic properties of wollastonite monoclinic polymorph

The structural, elastic, optical and electronic behavior of CaSiO3 monoclinic polymorph are estimated utilizing ultrasoft pseudo-potential technique operated in CASTEP code. The calculated lattice parameters, such as lattice constants, angle beta, and unit cell volume, are in excellent agreement with the experimental data. The computed elastic constant shows that CaSiO3 monoclinic is mechanical stable according to Born criteria. In addition, the polycrystalline properties such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy, compressibility and Debye temperature are determined based on the computed values of the elastic constants. Cauchy pressure and Poisson's ratio indicating a dominant ionic nature of the brittle CaSiO3 monoclinic. An Indirect band gap E (C-Gamma) = 5.02 eV, E (C-B) = 5.26 eV, and a direct gap E (Gamma-Gamma) = 5.06 eV were obtained. Finally, optical properties, such as dielectric function, absorption coefficient, refractive index, conductivity, loss function, and reflectivity have been predicted for polarized incident radiation with electrical vector. parallel to the crystalline b-axis.