关键词:  , 溴化镍, 密度泛函理论, 非共线磁结构, 电输运性质, 第一性原理, 各向异性

Abstract: We used multi-scale computational simulations to study the modulation mechanisms by which lattice strain regulated magnetic stability of monolayer NiBr₂, and analyzed the physical origins of its electronic structure and electrical transport anisotropy. We combined density functional theory (DFT)+U with Perdew-Burke-Ernzerhof (PBE) functional based PBE0 hybrid functional to accurately modify the electronic structure, determined the stable magnetic structure by using energy calcuations of PBE, and simulated the electrical conductivity (σ) and the Seebeck coefficient (S) at 300—900 K using AMSET to analyze the correlation between carrier concentration and transport behavior. The results show that when a lattice constant is 0.369 nm, the energy of the cycloidal spiral magnetic order is the lowest, which is consistent with the non-collinear magnetic order observed in the experiment. The band gap value of PBE0-calculated (3.60 eV) is same as the experimental value ((3.4±0.2)eV). σ exhibits extreme anisotropy, σ_a/σ_c≈125 at room temperature, σ_a/σ_c≈480 at 900 K, this is due to the extremely high vacuum potential barrier suppression along the c-axis. S exhibits a critical carrier concentration threshold in p-type doping, which reverses after exceeding the threshold (S_c>S_a). This is due to the saturation of the density-of-states gradient along the a-axis at high carrier densities and the enhanced contribution from dispersionless bands along the c-axis. These results reveal the anisotropy of electrical transport properties of monolayer NiBr₂, providing a theoretical foundation for the experimental exploration of low-dimensional magnetic semiconductor devices. 

Key words: nickel bromide, density functional theory, noncollinear magnetic structure, electrical transport property, first principles, anisotropy