First principles calculations for modern ceramic science and engineering

The free energy of compounds can be theoretically obtained as a function of temperature, pressure and chemical potentials by a combination of a first principles method including phonon calculations and statistical approaches using cluster expansion and Monte Carlo simulations. The information is quite useful in ceramic science and engineering since experimental data are not abundantly available. As an example of phonon calculations, results for graphite in comparison to diamond are presented. The free energy difference among polymorphs of Ga₂O₃ is shown as a function of temperature as well. Theoretical calculations of x-ray absorption near edge structures (XANES) and electron energy loss near edge structures (ELNES) are also demonstrated. Proper inclusion of the core–hole effect is mandatory in the calculation. For 3d transition element L_2,3 XANES/ELNES, a configuration interaction approach to take account of the correlation among the core–hole and the excited electron satisfactorily reproduces experimental spectra. As an example, results for Mn-doped ZnO are shown.