Thermodynamic stability of LaMnO3 and its competing oxides: A hybrid density functional study of an alkaline fuel cell catalyst

The phase stability of LaMnO3 with respect to its competing oxides is studied using hybrid-exchange density functional theory (DFT) as implemented in CRYSTAL09. The underpinning DFT total-energy calculations are embedded in a thermodynamic framework that takes optimal advantage of error cancellation within DFT. It has been found that by using the ab initio thermodynamic techniques described here, the standard Gibbs formation energies can be calculated to a significantly greater accuracy than was previously reported (a mean error of 1.6% with a maximum individual error of -3.0%). This is attributed to both the methodology for isolating the chemical potentials of the reference states, as well as the use of the Becke, three-parameter, Lee-Yang-Parr (B3LYP) functional to thoroughly investigate the ground-state energetics of the competing oxides.