Investigation of double perovskites Sr2SmNbO6 and X2CoNbO6 (X=Sr,Ba) with SCAN functional and plus U correction
Ying Zeng, Qingdan Hu, Min Pan, Kun Zhang, Salvatore Grasso, Chunfeng Hu, Qingguo Feng
Abstract
The double perovskites Sr2SmNbO6, Sr2CoNbO6 and Ba2CoNbO6 were investigated with first principles computations based on the density functional theory and plus U treatment. Firstly, different calculation methods were examined in order to quantitatively approach the exact band gap. It was found that neither the strongly constrained and appropriately normed (SCAN) semilocal density functional nor the hybrid HSE06 functional can well address the semiconducting nature of the investigated double perovskites, while PBE + U or SCAN + U with appropriately determining the U value can have good performance, which paves the way for future studies of double perovskites. With self-consistently calculated electron correlation strength, the magnetic states and the band gaps of the Sr2CoNbO6 and Ba2CoNbO6 were more precisely determined. The electronic, optical and thermoelectric properties were then investigated and discussed for possible applications.