Electronic structure, optical properties and band edges of layered MoO3: A first-principles investigation

Layered molybdenum trioxides with weak interlayer bonding and wide gap has attracted a lot of attention due to their rich technical application. Based on density functional theory, two layered molybdenum trioxides with orthorhombic (alpha-MoO3) and monoclinic (MoO3-II) structure have been investigated comparatively using several state-of-the-art functionals including optB88-vdW and HSE06. The structure, cleavage energy, electronic structure, optical properties and band edges have been given in details. Our results indicate that PBE overestimated the interlayer distance and underestimated the band gap seriously. The non-local optB88-vdW can predict a reasonable crystal structure and the HSE06 functional can give consistent band gap with experiment.The low cleavage energy calculated by optB88-vdW indicated that single layer MoO3 can be easily exfoliated from the bulk crystal. The electronic structure calculation indicate that in-plane atomic orbitals dominated the electronic states of valence band maximum (VBM) and the conduction band minimum (CBM). In addition, we also found that layered MoO3 have highly anisotropic optical adsorption behavior, which can be understood by the state-resolved distributions of electrons near VBM. Furthermore, the band edges of these two structures are also estimated by band gap center approximation, which are in good agreement with recent ultraviolet and inverse photoemission spectroscopy experiment. (C) 2017 Elsevier B.V. All rights reserved.