Electronic structure of second harmonic generation crystal Li₃VO₄ Available to Purchase

The origin of second harmonic generation (SHG) of Li₃VO₄ was investigated from the viewpoint of the band structure by using the tight‐binding method. The tight‐binding parameters were optimized to reproduce the density of states (DOS) obtained from x ray photoelectron spectroscopy and the optical band gap. Although Li₃PO₄ has the same crystal structure as Li₃VO₄, it shows no SHG. To explain the difference in optical nonlinearity we compared the electronic structures of Li₃VO₄ and Li₃PO₄, in particular at the bottom of conduction band (CB) and the top of valence band (VB), since they are known to play a primary role in SHG. In Li₃PO₄, the bottom of CB consists of P 3s and O 2p orbitals and the top of VB is composed of O 2p orbitals. These electronic structures result in a relatively low DOS at the bottom of CB and a wide band gap in Li₃PO₄. On the other hand, in Li₃VO₄, both bottom of CB and top of VB are composed of V 3d and O 2p. The preferential contribution of V 3d orbitals to the band edge states leads to a high DOS at the bottom of CB, a narrow band gap and delocalization of electrons on V–O bonds. We conclude that these electronic structures are responsible for the high optical‐nonlinearity of Li₃VO₄.