First-principles investigation of CaV2TeO8: a multifunctional heteroanionic oxychalcogenide for photocatalytic and thermoelectric applications

The development of industrial growth raises global energy demand. Novel materials with promising unorthodox features satiate and demand for sustainable, nontoxic, and cost-effective energy resources. In prospect to that, a first principles investigation was carried out to calculate the ground state and transport properties of CaV₂TeO₈ for thermoelectric and photocatalytic applications. In this investigation, CaV2TeO8 was mechanically stable at 1194.683 ų with a large elastic modulus of 117.95 GPa in the equilibrium state. To understand the electronic properties of CaV₂TeO₈ PBE-GGA exchange correlation was used to demonstrate the direct and indirect transition of a wide bandgap of 2.7–2.8 eV semiconducting nature. The optical properties of CaV₂TeO₈ include visible and UV absorption rage with energy of 2.8 eV. Further, to understand the properties of photogenerated charge carriers, the deformation potential theory was used to estimate the mobility of the charge carrier, Excitonic radius, and effective mass. Axial anisotropic strain in band degeneracy and shift in S-Y and Y-$\Gamma$ transition offers 3.17 Å of Frenkel type strongly bound exciton with a high carrier mobility of 2409.91 cm² V⁻¹ s⁻¹ electrons and 316.46 cm² V⁻¹ s⁻¹ holes, respectively. To estimate the feasibility of CaV₂TeO₈ in photocatalysis through the conduction and valence band edge under harsh pH conditions and various exchange correlations. The band edges of CaV₂TeO₈ show a halfway reaction of hydrogen evolution with reference to the Normal Hydrogen Electrode (NHE). The Boltzmann equation interface was also used to investigate the transport and thermoelectric properties. The results of the present study show a high Seebeck coefficient in CaV₂TeO₈ at 300 K and direct a thermoelectric figure of merit of 0.91. The high figure of merit and Seebeck coefficient at 300 K demonstrates CaV₂TeO₈ may suitable to flexible waste heat recovery system.