Role of spin-orbit coupling in the alloying behavior of multilayer Bi_(1-x)Sb_x solid solutions revealed by a first-principles cluster expansion

摘要

We employ a first-principles cluslcr-expansion method in combination with canonical Monte Carlo simulations to study the effect of spin-orbit coupling on the alloying behavior of multilayer Bi_(1-x)Sb_x, Our simulations reveal that spin-orbit coupling plays an essential role in determining the configurational thermodynamics of Bi and Sb atoms. Without the presence of spin-orbit coupling. Bi_(1-x)Sb_x is predicted to exhibit at low-temperature chemical ordering of Bi and Sb atoms, leading to formation of an ordered structure at .x≈0.5. Interestingly. the spin-orbit-coupling effect intrinsically induced by the existence of Bi and Sb results in the disappearance of chemical ordering of the constituent elements within an immiscible region existing at T ＜ 370 K. and consequently Bi_(1-x)Sb_x displays merely a tendency toward local segregation of Bi and Sb atoms, resulting in coexistence of Bi-rich and Sb-rich Bi_(1-x)Sb_x solid solutions without the formation of any ordered structure of Bi_(1-x)Sb_x as predicted in the absence of spin-orbit coupling. These findings distinctly highlight an influence of spin-orbit coupling on the alloying behavior of Bi_(1-x)Sb_x and probably other alloys composed of heavy elements, where the spin-orbit-coupling effect is supposed to be robust.