Stannous oxide (SnO), an exclusive p-type oxide semiconductor in the oxide family, is a source of renewed interest because of its ability to be an excellent anode material. So far, there are very few reports on the vibrational propertiesof SnO and controversy remains in the assignment of vibrational modes. Textured single crystals of SnO were synthesized by a one-step solvothermal method. The as-synthesized SnO crystals have a wide (001) plane, as confirmed by high resolution transmission electron microscopy images. Raman spectroscopy is used for the identification of phase as well as crystalline orientation. Moreover, a unique assignment of phonon modes in SnO is also performed using polarized Raman spectroscopic studies for different orientations around c-axis of the crystalwith the incident electric field vector. Thus, a novel methodologyof phonon assignment is adopted with a minimum amount of data collection for a diatomic molecule having a tetragonal symmetry with a number of symmetry elements.

The aim of this study is to investigate the crystal structure stability of UO$_2$ upon applying pressure using an evolutionary algorithm. UO$_2$ exhibits face-centred cubic crystal structure with space group $Fm\bar{3}m$ (S.G. No. 225) in the ambient pressure, and above 82 GPa transforms to an orthorhombic structure with space group Pnma (S.G. No. 62). The first-order structural phase transition is accompanied by a 5.4% volume collapse. The lattice parameters of both the cubic and orthorhombic phases decrease with the applied pressure. The bulk modulus ($B_o$) and the pressure derivative of bulk modulus ($B'_{o}$) values of the cubic phase were found to be 210.41 ± 0.22 GPa and 3.60 ± 0.01, respectively. The $B_o$ and $B'_{o}$ values of the orthorhombic phase were found to be 218.09 ± 3.29 GPa and 3.64 ± 0.03, respectively. The enthalpy of formation linearly increases with the applied pressure for both the cubic and orthorhombic phases, and at 82 GPa theenthalpy of the orthorhombic phase is found to be lower than the cubic phase indicating the structural phase transition.