On the role of the exact Hartree–Fock exchange in determining the Jahn–Teller energy splitting and electronic band gap in the KBF3 (B=Sc, Ti, Fe, Co, Cr and Cu) perovskites. A quantum mechanical investigation

Abstract

KBF3 perovskites present a partially filled t2g (Sc, Ti, Fe or Co), or eg (Cr or Cu) subshell. The role of the adopted functional on the Jahn–Teller (JT) splitting, band gap, and cell deformation is investigated. Results obtained with PBE, HSE06, B3LYP, PBE0, Hartree–Fock and a new functional PBE(X), in which X is the percentage of HF exchange (0 to 100%) are compared, revealing that the JT splitting and energy gap depend dramatically on X, while the correlation and local exchange terms composing the functionals have a slight influence on the investigated properties.