Ab Initio Quantum Dynamics Simulation of the Impact of Graphene on the Carrier Lifetime of the ZnV2O6 Photocatalyst.

We used a nonadiabatic molecular dynamics simulation to determine the carrier dynamics of a graphene/ZnV2O6 heterostructure in the search for an effective photocatalyst material. The C-2p orbital promotes the wave function overlap, guiding electrons to move between graphene and ZnV2O6, successfully achieving good mixing with the valence and conduction bands in ZnV2O6 materials, which is conducive to supporting carrier migration. The overlap between graphene/ZnV2O6 electrons and hole wave functions is less than that of ZnV2O6, and there is small absolute nonadiabatic coupling. The charge separation caused by graphene increases the carrier lifetime and prevents nonradiative electron-hole recombination. This study reveals the microscopic mechanism of extending the carrier lifetime of ZnV2O6 by introducing graphene, providing useful insights for regulating the electronic structure, promoting electron transfer and ultrafast electron and hole transfer. This strategy provides design considerations for advanced photocatalytic materials.

First principles calculation of the ZnV2O6(001) surface terminations: the thermodynamic stability and electronic structure study.

We have investigated the surface structure and relative stability of ZnV2O6(001) using a thermodynamic technique based on density functional theory (DFT). We built Zn-V-O surface phase diagrams of various surface terminations using the obtained surface Gibbs free energy. In this study, we selected nine different surface terminations along the (001) crystal plane to elucidate that the E, G, H, and I terminations (as shown in Table 1) are the most stable configurations. We found that although their stability varies widely, the four terminations on the ZnV2O6(001) surface can be stabilized under specific thermodynamic equilibrium circumstances. Furthermore, we calculated the surface electronic structures of the four surface terminations and found that there are surface states conducive to visible light absorption at the G, H, and I terminations. The different termination structures are significant in improving the range and intensity of light absorption of ZnV2O6 in specific regions. The fact that the work functions fluctuate significantly for different surface terminations suggests that the work function of ZnV2O6 can be changed to increase photocatalytic activity by achieving thermodynamically favored surface terminations under appropriate conditions. The obtained surface phase diagram will further lay a foundation for the study of the ZnV2O6 surface. These results may help to explore the inherent properties of the ZnV2O6 surface and provide useful strategies for future experimental research on ZnV2O6-based photocatalysts.

First-Principles Study on the Direct Bandgap Double Perovskite Series Cs2LiInX6(X = F, Cl, and Br).

A molecular crystal structure model of the lead-free halide chalcogenide semiconductor Cs2LiInX6 (X = F, Cl, and Br) was established, and its energy band, density of states, optical properties, and thermodynamic properties were calculated using the first nature principle and the effect of different pressures on the bandgap of Cs2LiInX6 (X = F and Cl, Cs2LiInF6 with a bandgap of 7.359 eV, Cs2LiInCl6 with a bandgap of 5.098 eV, and Cs2LiInBr6 with a bandgap of 3.755 eV). The absorption of light is mainly due to the transition of halide ions from p- to s-orbitals. The p- and In-s orbitals of halide ions play a major role in light harvesting. Cs2LiInCl6 has low sensitivity to relative pressure and is stable at a 0-100 GPa pressure. In the structure of Cs2LiInX6 (X = F, Cl, and Br), changing the halogen atom can effectively improve its optical properties. Cs2LiInCl6 and Cs2LiInF6 are considered as the most promising candidates for UV detectors. Cs2LiInF6 has a large forbidden band width and a high Debye temperature and shows a high photoluminescence quantum yield in the field of phosphors with great potential in the field of phosphors with high photoluminescence quantum yields. This study is a positive reference for the preparation of lead-free chalcogenide-type ultraviolet detectors with excellent performance.