Study for material analogs of FeSb₂: material design for thermoelectric materials

Using the \emph{ab initio} evolutionary algorithm (implemented in USPEX) and electronic structure calculations we investigate the properties of a new thermoelectric material FeSbAs, which is a material analog of the enigmatic thermoelectric FeSb$_{2}$. We utilize the density functional theory and the Gutzwiller method to check the energetics. We find that FeSbAs can be made thermodynamically stable above $\sim$30 GPa. We investigate the electronic structure and thermoelectric properties of FeSbAs based on the density functional theory and compare with those of FeSb$_{2}$. Above 50 K, FeSbAs has higher Seebeck coefficients than FeSb$_{2}$. Upon doping, the figure of merit becomes larger for FeSbAs than for FeSb$_{2}$. Another material analog FeSbP, was also investigated, and found thermodynamically unstable even at very high pressure. Regarding FeSb$_{2}$ as a member of a family of compounds (FeSb$_{2}$, FeSbAs, and FeSbP) we elucidate what are the chemical handles that control the gaps in this series. We also investigate solubility (As or P for Sb in FeSb$_{2}$) we found As to be more soluble. Finally, we study a two-band model for thermoelectric properties and find that the temperature dependent chemical potential and the presence of the ionized impurities are important to explain the extremum in the Seebeck coefficient exhibited in experiments for FeSb$_{2}$.