A DFT study on the electronic structure of tungsten trioxide polymorphs.

Tungsten trioxide (WO3) is an intermediate product in the recovery of tungsten from its minerals. Recently, it has attracted increasing attention due to its exclusive structural properties and its high potential in electronic applications. The crystal lattice of tungsten trioxide is highly dependent on temperature. In this paper we investigated the equilibrium structure of tungsten trioxide in four crystal systems, i.e. monoclinic system, tetragonal system, orthorhombic system, and cubic system. We did our first principle calculations using a pseudopotential model based on the spin dependent density functional theory and implementing generalized gradient approximation for exchange correlation energy. In each case, we calculated total energy, Fermi energy, band structure, and density of states and then we made comparisons. The results show that WO3 is a semiconductor in all four crystal structures with zero total magnetization. Moreover, tungsten trioxide has a direct band gap in the range of visible wavelength that improves its optical applications potentially. [ABSTRACT FROM AUTHOR]