Energetics of phase transitions in BaO through DFT calculations with norm-conserving pseudopotentials: LDA vs. GGA results

We present DFT calculations for barium monoxide (BaO) in its four different allotropic forms, in order to study the energetics of structural phase transitions in this system. We find that LDA is unable to determine the correct sequence of structural transitions, while GGA reproduces it correctly. Results for the energetics of the system are presented along with transition pressures at 0 K, in reasonable agreement with ultrasoft pseudopotential calculations. Our study shows that the use of GGA is fundamental for an adequate description of the energetics of phase transitions in BaO.