Mechanical and thermodynamical stability of BiVO ₄ polymorphs using first-principles study

Abstract

First principles calculations of structural, electronic, mechanical, and thermodynamic properties of different polymorphs of BiVO 4 are performed using Bender-type plane/wave ultrasoft pseudopotentials within the generalized gradient approximation (GGA) in the frame of density functional theory (DFT). The calculated structural and electronic properties are consistent with the previous theoretical and experimental results. The electronic structures reveal that m-BiVO 4 , op-BiVO 4 , and st-BiVO 4 have indirect band gaps, on the other hand, zt-BiVO 4 has a direct band gap. From the DOS and Mulliken's charge analysis, it is observed that only m-BiVO 4 has 6s 2 Bi lone pair. Bond population analysis indicates that st-BiVO 4 shows a more ionic nature and a similar result is obtained from the elastic properties. From the elastic properties, it is observed that st-BiVO 4 is more mechanically stable than the others. st-BiVO 4 is more ductile and useful for high electro-optical and electro-mechanical coupling devices. Our calculated thermodynamic properties confirm the similar characteristics found from electronic and elastic properties. m-BiVO 4 is useful as photocatalysts, solid state electrolyte, and electrode and other polymorphs are applicable in electronic device fabrications.

Phase Transitions of BiVO4 under High Pressure and High Temperature

“…They also agree with the results reported by Hazen and Mariathasan . This agreement and the quasi-hydrostatic conditions of our experiments suggest that the bulk modulus of scheelite-type BiVO 4 has been underestimated by the experiments of Cheng et al and the calculations of Farid Ul Islam et al In the fergusonite structure, there is again an excellent agreement between our results and the results reported by Hazen and Mariathasan . In this case, computer simulations largely overestimate the bulk modulus.…”

“…4 This agreement and the quasi-hydrostatic conditions of our experiments suggest that the bulk modulus of scheelite-type BiVO 4 has been underestimated by the experiments of Cheng et al 17 and the calculations of Farid Ul Islam et al 37 In the fergusonite structure, there is again an excellent agreement between our results and the results reported by Hazen and Mariathasan. 4 In this case, computer simulations 37 largely overestimate the bulk modulus. For the zircon structure, our bulk modulus is around 20−30% smaller than the results reported by Cheng et al 17 and Farid Ul Islam et al 37 However, we are confident in our bulk modulus for several reasons.…”

“…The corresponding EOSs are plotted in Figures and . In Table , our EOS parameters are compared with the results of previous experiments , and calculations . The fit to the zircon data yielded two incompatible values for the bulk modulus.…”

“…In Table 3, our EOS parameters are compared with the results of previous experiments 4,17 and calculations. 37 The fit to the zircon data yielded two incompatible values for the bulk modulus. In fact, the two volume curves represented with solid symbols in Figure 6, lower panel, clearly have different slopes.…”

Phonon anharmonicity: a pertinent review of recent progress and perspective

“…For example, for an ns 2 np m valence configured atom, if the valence electron of np orbitals alone participate in bonding with the anion, the bond will not share the ns 2 electrons and lead the ns 2 electron pair to an isolated ("lone pair") state, hence form the LPEs. The LPEs induce strong anharmonicity in various materials, such as binary oxides [150][151][152], binary chalcogenides [39,[153][154][155], ternary oxides [156,157], ternary chalcogenides [142,148,158,159]. SnSe is a typical example to show this issue due to the active 5s 2 lone pair electrons of Sn atoms, visualized by the "caps" in the space between bilayers in Figure 15 Consequently, such orbitally driven giant anharmonicity acts as the primary origin of the ultralow thermal conductivity in SnSe.…”