Narrow Results

Based on the first-principles method of density functional theory and the transition state theory, the adsorption, occupancy and diffusion behaviors of H atoms in LaFeO₃(010) surface with O vacancy are investigated. It is found that, for the LaFeO₃(010) surface with O vacancy, the H atom prefers to adsorb on the O atom and also could adsorb on the Fe atom; the adsorption energy of H atom in the surface layer is the biggest, while the adsorption energy decreases with the H atom in-depth diffusion to the bulk; the diffusion of H atoms from the surface layer to the bulk phase is a process of progressive rotation around the O atom, and the stepwise diffusion is more likely to occur than the direct diffusion. If the H atom can cross the barrier and diffuse from the surface to the subsurface, it will be more likely to diffuse inward. The presence of O vacancy can reduce the barrier for H atoms diffusion from the surface to the subsurface, and then improve the diffusion properties of the LaFeO₃(010) surface system.

In this paper, the plane wave ultra-soft pseudopotential method was performed to analyze the effect of neutral Zn vacancy (V${}_{\mathrm{\text{Zn}}}$) and O vacancy (V${}_{\mathrm{\text{O}}}$) on the electronic and magnetic properties of Mn-doped ZnO systems. In a $2\times 2\times 2$ ZnO:Mn supercell, the sites of V${}_{\mathrm{\text{Zn}}}$ and V${}_{\mathrm{\text{O}}}$ were set as nearest neighbor, next nearest neighbor and far nearest neighbor relative to Mn site, respectively. The results indicated that V${}_{\mathrm{\text{Zn}}}$ is easier to be produced than V${}_{\mathrm{\text{O}}}$ in the ZnO:Mn system, and both kinds of defects are more likely to be generated in the nearest neighbor of Mn site. Meanwhile, the ZnO:Mn-V${}_{\mathrm{\text{Zn}}}$ system is p-type conductive. The farther the distance between V${}_{\mathrm{\text{Zn}}}$ and Mn, the better the conductivity of the system. Contrary to V${}_{\mathrm{\text{Zn}}}$, the ZnO:Mn-V${}_{\mathrm{\text{O}}}$ system is n-type conductive. The farther the distance between V${}_{\mathrm{\text{O}}}$ and Mn, the worse the conductivity of the system. Furthermore, the ZnO:Mn systems containing neutral V${}_{\mathrm{\text{Zn}}}$ or V${}_{\mathrm{\text{O}}}$ are both likely to be in antiferromagnetic phase. However, the presence of V${}_{\mathrm{\text{Zn}}}$ will enhance the possibility, while V${}_{\mathrm{\text{O}}}$ will weaken it.

In this work, the electronic structure and optical properties of Zr-doped $\beta$-Ga₂O₃ with interstitial H and O vacancies were studied by using first-principles generalized gradient approximation combined with the Hubbard U method based on density functional theory. The energy band structure, density of states, absorption spectrum, effective mass, mobility and conductivity of the doped system were calculated and analyzed. Results showed that the doped system was more stable under the Ga-rich condition than under the O-rich condition. With the increase in Zr doping concentration, the bandgap of the $\beta$-Ga₂O₃ system gradually narrowed and the absorption spectrum of the system blue-shifted in the wavelength range of 162–275nm. System conductivity was enhanced by Zr doping, decreased by O vacancies and greatly improved by interstitial H. Therefore, doping Zr into the $\beta$-Ga₂O₃ system is important for improving material properties and preparing electronic and optical devices.