We report the results of a comprehensive study on the structural, electronic, and optical properties of ${\mathrm{Ga}}_2{\mathrm{O}}_3$ in its ambient, monoclinic $\left(\beta \right)$ and high-pressure, hexagonal $\left(\alpha \right)$ phases in the framework of all-electron density functional theory. In both phases, the conduction band minimum is at the zone center while the valance band maximum is rather flat in the $k$ space. The calculated electron effective mass $m_e^{*}∕m_0$ comes out to be 0.342 and 0.276 for $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ and $\alpha \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$, respectively. The dynamic dielectric function, reflectance, and energy-loss function for both phases are reported for a wide energy range of $0–50\mathrm{eV}$. The subtle differences in electronic and optical properties can be attributed to the higher symmetry, coordination number of Ga atoms, and packing density in $\alpha \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$ relative to that in $\beta \text{−}{\mathrm{Ga}}_2{\mathrm{O}}_3$.

We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density-functional theory framework, with additional calculations utilizing Hartree-Fock plus second-order Møller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: $\mathrm{G}>\mathrm{A}\approx \mathrm{T}\approx \mathrm{C}>\mathrm{U}$, with the equilibrium configuration being rather similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step toward a first-principles understanding of how the base sequence of DNA can affect its interaction with carbon nanotubes, as observed experimentally.

The emergence of two-dimensional (2D) materials has led to tremendous interest in the study of graphene and a series of mono- and few-layered transition metal dichalcogenides (TMDCs). Among these TMDCs, the study of molybdenum disulfide (MoS₂) has gained increasing attention due to its promising optical, electronic, and optoelectronic properties. Of particular interest is the indirect to direct band-gap transition from bulk and few-layered structures to mono-layered MoS₂, respectively. In this review, the study of these properties is summarized. The use of Raman and Photoluminescence (PL) spectroscopy of MoS₂ has become a reliable technique for differentiating the number of molecular layers in 2D MoS₂.

The physical and chemical properties of phosphorene oxide including its formation by oxygen adsorption on the bare phosphorene was investigated.