Hydrogen and water adsorptions on the monolayer hexagonal boron nitride (h-BN) have been studied using the density functional theory. In this study, two configurations of monovacancy were modeled, i.e., monovacancy at the nitrogen site (VN) and monovacancy at the boron site (VB), by removing N and B atoms from the h-BN sheet, respectively. A supercell consisting of 32 atoms was used to analyze the adsorption of hydrogen and water (H2O) by calculating formation and adsorption energies. From the calculated negative adsorption energies, we found that the involved reactions are exothermic, meaning that hydrogen and H2O are easily adsorbed on the h-BN sheet. In addition, the hydrogen system at the VB site was the most stable, as shown by the lowest formation energy of 2.78 eV.
In this study, electronic structure calculations of Ca-intercalated bilayer graphene are conducted using the density functional theory (DFT). We modeled two configurations by positioning calcium in the middle of the bilayer (M-site) and on top of the bilayer surface (T-site). Our results show that the Dirac point is shifted below the fermi level. The approximated critical temperature is 7.9 K. We then calculated the electron transfer and formation energy for each system. We found that, for the M-site, the electron transfer increased as the Ca concentration increased, while the reverse occurred for T-site. The calculated formation energies were negative, meaning that all configurations were spontaneously created. In other words, the involved reactions were exothermic.
We perform the density functional theory calculations (DFT) to study the effect of biaxial strain on the band structures of monolayer GaN. We apply compressive and tensile strains up to 10%. There is no change of bandgap for the applied tensile strains below 8%. The compressive strains have a constant bandgap which is slightly smaller than that of the zero strain. We find that the applied tensile strain above 8% affects its electronic structure and decreases its bandgap energy by about 0.05 eV while the compressive strain above 4% decreases its bandgap about 0.22 eV.
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