First-Principles Study on Polymorphs of AgVO₃: Assessing to Structural Stabilities and Pressure-Induced Transitions

In this paper, we present a comprehensive theoretical study, based on density-functional theory calculations, and which focuses on the structural and electronic properties of silver vanadium oxide (AgVO 3 ) in the monoclinic [ Cm (β-AgVO 3 ), C 2 /c (α-AgVO 3 ), and Cc ], orthorhombic ( Amm 2), and cubic ( Pm 3̅ m ) phases from 0–30 GPa. The structural and electronic properties, the stability of different phases, and the pressure-induced solid–solid phase transitions of AgVO 3 have been previously studied. The effects of pressure on the band structures, energy–gap values, density of states, and vibrational frequencies are also studied. Numerical and analytical calculations are conducted to obtain the lattice parameters, the bulk modulus K and their pressure derivative K ′, and the energy-volume equations of state. The influence of different parametrizations of the exchange-correlation functional (B3LYP, HSE06, and PBE) on the investigated properties is analyzed, and the results are compared to available experimental data. For the first time, a complex and unexpected structural and chemical behavior as a function of pressure is reported. The β-phase is the most stable and the first phase transition between the monoclinic β-AgVO 3 and Cc phase takes place at 5 GPa (B3LYP), 3 GPa (HSE06), and 2 GPa (PBE). There are pressure-induced transitions among the β-, α-monoclinic, and cubic structures, and the corresponding values for the pressure transitions are dependent on the functional used. Two new polymorphs, monoclinic Cc and orthorhombic ( Amm 2), have been characterized for the first time, and their contrasting structural stabilities as well as their transition mechanisms can be understood from the intrinsic characteristics of the crystal lattices. The Badger’s rule is fulfilled for Cm, Amm 2, and Pm 3̅ m polymorphs, while it is invalid for the C 2/ c and Cc phases. Theoretical results show that the studied reactive channels from β-AgVO 3 toward binary oxides, Ag 2 O and V 2 O 5, AgO and VO 2; the elements Ag, V and O 2; silver pyrovanadate, Ag 4 V 2 O 7 and V 2 O 5, as well as Ag 2 V 4 O 11 and Ag 2 O are not thermodynamic favorable processes at pressures up to 30 GPa. These results contribute to the understanding of the pressure behavior of AgVO 3 -based compounds. In addition, it would be interesting to determine whether further measurements and calculations would confirm the predicted structural and thermodynamic properties as well as the solid-state transformations of AgVO 3 polymorphs, which have not yet been experimentally shown.