First-Principles Studies of Perovskite Compounds for Thermoelectric Applications

Computational modeling techniques have been used to provide detailed insights into the structure-property relationships of materials. We have collaborated with the National Institute of Standards and Technology to develop various perovskite compounds with desired thermoelectric properties. We have used density functional theory-based approaches to study structural stability and electrical properties of R ₂ (FeCo)O ₆ perovskite compounds (R = Pr, Nd, Sm, Eu and Gd), for which Fe and Co randomly occupy the B-site. Vienna ab-initio simulation package (VASP) has been performed to optimize geometry and structure. Superlattice and locally disordered phases have been compared through a total energy minimization approach. We predict that a disordered phase exhibits a lower free energy than that of a superlattice. We have supplied initial magnetic moments of 4µ _B and 1µ _B for Fe and Co, respectively. A 4x4x4 gamma-centered k-points mesh has been applied to sample a Brillouin zone. Additional inputs include a conjugate electronic minimization algorithm and a 400 eV cutoff energy for plane-wave basis set. In order to validate our prediction, theoretical lattice parameters and volumes have been compared with experimental results. We have calculated electronic density of states for the stable phases and have briefly explored the methodology of estimating electrical conductivity properties.