Semi-conducting alloys BiSb have emerged as a potential candidate for topological insulators and are well known for their novel thermoelectric properties. In this work, we present a systematic study of the low-energy phases of 35 different compositions of BiSb (0 < x < 1) at zero temperature and zero pressure. We explore the potential energy surface of BiSb as a function of Sb concentration by using the ab initio minima hopping structural search method. Even though Bi and Sb crystallize in the same R3[combining macron]m space group, our calculations indicate that BiSb alloys can have several other thermodynamically stable crystal structures. In addition to the configurations on the convex hull, we find a large number of metastable structures which are dynamically stable. The electronic band structure calculations of several stable phases reveal the presence of strong spin-orbit interaction leading to the Rashba-Dresselhaus spin-splitting of bands which is of great interest for spintronics applications. We also find an orthorhombic structure of BiSb in the Imm2 space group which exhibits signatures of type-II Weyl semimetal. Additionally, we have studied the thermoelectric properties of the selected structures. Regarding thermoelectric properties, we find that the compositions which crystallize in the rhombohedral structure exhibit values of the Seebeck coefficient and the power factor similar to that of BiTe at room temperature, while the theoretical maximum figure of merit (ZT) is smaller than that of BiTe. We observe enhancement in the thermopower with the increase in the strength of the Rashba-Dresselhaus spin-splitting effect.

We use first-principles calculations to understand the behavior of the Seebeck coefficient (S) in Bi 2 Te 3 as a function of isotropic pressure. We perform calculations up to 5 GPa using density functional theory and with thermoelectric properties extracted using Boltzmann transport equations. We find that with the increase in pressure the system becomes more metallic, in agreement with previous calculations on Sb 2 Te 3 . For p-type doping the overall behavior is a decrease in S with an increase in pressure. At small values of hole doping (p = 1.8 × 10 18 cm −3 ), we obtain an anomalous variation of S under 2 GPa, which is an indication of the electronic topological transition. For n-type doping, S slightly increases with pressure.

We have combined a neural network formalism with metaheuristic structural global search algorithms to systematically screen the Mg–Ca binary system for new (meta)stable alloys.