where W is the number of microstates and is related to the concentration of defect X (c X ) with potential microstates N states . Accounting for the reduction in the configurational entropy upon complex association, and employing the assumptions of (i) equal N states for point and complex defects and (ii) majority and minority constituent point defects (c B ≫ c A ), a high degree of complex association (c AB ≥ c A ) is expected when the magnitude of the association energy (|∆H|) is larger than the entropic cost (-T ∆S), approximated by the critical association energy ∆E crit : 82