Constant Pressure Molecular Modeling of Six Optimised Titanium Oxide Polymorphs: Metal Oxide Semiconductors

Abstract

Six polymorphs of Titania which include Rutile, Anatase, Brookite, high-pressure Brookite, the columbite-type TiO2-II and Corundum-like type CLT, have been modelled under constant pressure using the General Utility Lattice Program (GULP) with results comparing favourably with the classical and long standing molecular dynamics model by Matsui and Akaogi (1991). Using energy (Buckingham potential model) minimization criteria with no need for thermal expansivity correction, the simulation yielded satisfactory mechanical and thermodynamic properties, and produced stable optimized nanoparticle for the polymorphs investigated except the CLT. Our procedure and results were validated by conducting a Molecular Dynamic optimization for all six polymorphs and using the Broyden-Fletcher-Goldfarb-Shanno: BFGS optimizer with a secondary switch to Rational Functional Optimization- RFO with satisfactory results. Our simulations suggests that enhanced performances for wide-bandgap semiconductors and of photovoltaic cell electrodes can be a reality with lower heat capacity Titania polymorphs.