Theoretical investigation to thermal equilibrium concentration of point defect through first-principles calculation

First-principles calculations based on density functional theory enable us to quantify the thermal equilibrium concentration of a point defect through calculating the formation energy of the defect. In order to know the formation energy, we need three parameters: the energy difference between defective and perfect systems, chemical potential of constitutive atoms and Fermi level. The energy difference is obtained from calculations based on “supercell method”. The energy of a supercell with a charged defect should be corrected by an appropriate way such as alignment of electrostatic potential. The chemical potential and Fermi level can be fixed from conditions of phase equilibrium and charge neutrality.