Orthovanadates are a peculiar type of compound because of the unique crystal structures that are observed. Altering the size of the A-site atom has shown that orthovanadates can assume both monoclinic and tetragonal forms in normal conditions. An irreversible tetragonal zircon (space group: I41/amd) to tetragonal scheelite (space group: I41/a) phase transition is observed in the case of zircon type compounds with small-sized cations [1–3]. These are comprised of HoVO4, EuVO4, TbVO4, SmVO4, and LuVO4 at pressures of 6−8 GPa. Another reversible scheelite to fergusonite (space group: I41/a) transition is observed at higher pressures. NdVO4 at 18.1 GPa and CeVO4 at 14.7 GPa show a second reversible transition from the fergusonite to an orthorhombic phase [4,5]. This property, coupled with its unique electronic structure, makes them a fascinating class of materials. Orthovanadates have been found to have considerable use in various fields. Lanthanide orthovanadates are indispensable as catalysts, polarizers, solid-state protonic conductors, phosphors, and low threshold laser hosts. These materials illustrate attractive magnetic, thermally activated, optical, and x-ray luminescent properties. Considerable research has been performed on lanthanum orthovanadate, LaVO4, attributed to its surface catalytic properties. LaVO4 exist in monoclinic monazite crystal structure under normal circumstances, which is in contrast with the rest of the rareearth orthovanadates that exist in a zircon state. The coordination number of Ln3+ is “8” in the tetragonal zircon structure and “9” in the monoclinic monazite structure. This aberration in the crystal structure of LaVO4 is attributed to the larger size of La3+ compared to the rest of the rare-earth ions. This is due to the lower effective charge (leading to less electrostatic force on the surrounding electrons) and less efficient shielding by f -shell electrons in the case of the remaining rare-earth elements (Lanthanide contraction). Samarium orthovanadate, SmVO4, exists in the tetragonal zircon phase (space group: I41/amd) under ambient conditions. Like other rare-earth orthovanadates, SmVO4 has been a material of intrigue from the various applications it has, from being used as catalysts [6], optical polarizers [7], solar cells [8] to gas sensors [9], and thin-film phosphors [10]. The effect of pressure and the accompanying metastable phase transformation of SmVO4 has been studied [6]. A study on the pressure-induced phase transformation in zircon-type orthovanadate SmVO4 from experiment and theory has been conducted in the recent past [11]. Alternate routes for the synthesis of SmVO4 via hydrothermal method mediated by a chelating ligand using decavanadate as the source of vanadium have also been studied [12]. The theoretical approach has rarely been employed in RVO4 compounds. Density functional theory (DFT) is widely used for first-principles studies of crystalline materials. DFT provides considerable insight into the lattice dynamics of the compounds. In SmVO4, the phase obtained at ambient and the temperatures explored in this study are stable at T ∼0 K; hence the issue of stabilizing the phase is not a concern, and the DFT studies can be used to analyze the experimental data in detail. This work is focused on intertwining the experimental data obtained from the experiments performed, and the theoretical calculations performed using DFT, including the phonon modes, phonon lifetimes, and the band-gap variation with temperature. The infrared (IR) and Raman spectroscopy are used to study the crystallinity collectively with the DFT methods. An image can be generated, which would further enhance the idea derived. A temperature-induced crystallinity is linked with the vibrational properties of SmVO4, with several experimental measurements and theoretical explanations.
Orthovanadates are a peculiar type of compound because of the unique crystal structures that are observed. Altering the size of the A-site atom has shown that orthovanadates can assume both monoclinic and tetragonal forms in normal conditions. An irreversible tetragonal zircon (space group: I41/amd) to tetragonal scheelite (space group: I41/a) phase transition is observed in the case of zircon type compounds with small-sized cations [1–3]. These are comprised of HoVO4, EuVO4, TbVO4, SmVO4, and LuVO4 at pressures of 6−8 GPa. Another reversible scheelite to fergusonite (space group: I41/a) transition is observed at higher pressures. NdVO4 at 18.1 GPa and CeVO4 at 14.7 GPa show a second reversible transition from the fergusonite to an orthorhombic phase [4,5]. This property, coupled with its unique electronic structure, makes them a fascinating class of materials. Orthovanadates have been found to have considerable use in various fields. Lanthanide orthovanadates are indispensable as catalysts, polarizers, solid-state protonic conductors, phosphors, and low threshold laser hosts. These materials illustrate attractive magnetic, thermally activated, optical, and x-ray luminescent properties. Considerable research has been performed on lanthanum orthovanadate, LaVO4, attributed to its surface catalytic properties. LaVO4 exist in monoclinic monazite crystal structure under normal circumstances, which is in contrast with the rest of the rareearth orthovanadates that exist in a zircon state. The coordination number of Ln3+ is “8” in the tetragonal zircon structure and “9” in the monoclinic monazite structure. This aberration in the crystal structure of LaVO4 is attributed to the larger size of La3+ compared to the rest of the rare-earth ions. This is due to the lower effective charge (leading to less electrostatic force on the surrounding electrons) and less efficient shielding by f -shell electrons in the case of the remaining rare-earth elements (Lanthanide contraction). Samarium orthovanadate, SmVO4, exists in the tetragonal zircon phase (space group: I41/amd) under ambient conditions. Like other rare-earth orthovanadates, SmVO4 has been a material of intrigue from the various applications it has, from being used as catalysts [6], optical polarizers [7], solar cells [8] to gas sensors [9], and thin-film phosphors [10]. The effect of pressure and the accompanying metastable phase transformation of SmVO4 has been studied [6]. A study on the pressure-induced phase transformation in zircon-type orthovanadate SmVO4 from experiment and theory has been conducted in the recent past [11]. Alternate routes for the synthesis of SmVO4 via hydrothermal method mediated by a chelating ligand using decavanadate as the source of vanadium have also been studied [12]. The theoretical approach has rarely been employed in RVO4 compounds. Density functional theory (DFT) is widely used for first-principles studies of crystalline materials. DFT provides considerable insight into the lattice dynamics of the compounds. In SmVO4, the phase obtained at ambient and the temperatures explored in this study are stable at T ∼0 K; hence the issue of stabilizing the phase is not a concern, and the DFT studies can be used to analyze the experimental data in detail. This work is focused on intertwining the experimental data obtained from the experiments performed, and the theoretical calculations performed using DFT, including the phonon modes, phonon lifetimes, and the band-gap variation with temperature. The infrared (IR) and Raman spectroscopy are used to study the crystallinity collectively with the DFT methods. An image can be generated, which would further enhance the idea derived. A temperature-induced crystallinity is linked with the vibrational properties of SmVO4, with several experimental measurements and theoretical explanations.
