The magnetic properties of Ni-doped WS2 monolayer are investigated using first-principles method. The results indicate that both one-Ni-doped and the nearest two-Ni-doped systems are magnetic. The p-d hybridization between the Ni atom and its neighboring S atoms results in the ferromagnetic interaction of the Ni-doped WS2 monolayer. The antiferromagnetic coupling is observed with increasing Ni-Ni distance which can be explained by two-impurity Haldane-Anderson model using quantum Monte Carlo method. Our studies show that the nearest two Ni-doped WS2 monolayers to be candidates for two-dimensional transition-metal nanosheets. Moreover, we discussed the differences in the formation energy between W-rich and S-rich conditions. Our results also predict that it would be easier to incorporate Ni atoms into a S-rich WS2 monolayer in the experiment.
The electronic properties of the GeC bilayer with different stacking patterns are investigated using density functional theory. A different behavior shows up when applying normal strain and electric field (E-field). Under normal strain, the bandgap becomes very elastic and presents an indirect-to-direct bandgap transition. By applying the E-field, the intrinsic bandgap swiftly reduces to zero. The major modulation of the bandgap is mainly due to the migration of Ge-p orbitals in the conduction band. Our results reveal the flexible electronic properties of the GeC bilayer, which would provide a theoretical reference for the development of the GeC bilayer.
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