Detailed ab-initio studies on electronic structure and optical properties have been carried out for orthovanadates, and periodate compounds, ScVO4, YVO4, LuVO4, and NaIO4, KIO4, RbIO4, CsIO4 based on the Full potential linearized augmented plane wave method within the frame work of Density Functional Theory using Tran and Blaha modified Becke Johnson potential (TB-mBJ). We have compared the optical properties of orthovanadates with periodates, and also with its high pressure phase. The main difference observed in moving from orthovanadates to periodates is the increase in band gap, and bands turn out to be less dispersive. By considering all these facts, we predict orthovanadates to be better scintillators than periodates, which is well explained from the band structure, and optical properties calculations. In addition, we also compared the optical properties of orthovanadates at ambient, and high pressure and we observed a decrease in the band gap of orthovanadates, increase in valence band width at high pressure when compared to ambient phase. Tuning the band gap, which is an important criteria for scintillators, can be observed in orthovanadates by decreasing the cation size, and also by moving to the high pressure scheelite phase. High pressure phase of orthovanadates might be more favourable as the zircon to scheelite transition is irreversible, and the transition pressure is also less around 8 GPa. (C) 2015 Elsevier B.V. All rights reserved.