Energy Functional

The energy functional consists of coulomb, kinetic and exchange-correlation (xc) terms. The starting point for the xc functional is usually the result for the homogeneous electron gas, after which so called nonlocal or generalized gradient corrections (GGA: Generalized Gradient Approximation) are added. See the keys Spin and XC.

The program calculates by default the self-consistent field solution from the potential in the spin-restricted local density approximation (LDA) to the exchange-correlation (XC) potential. The post-SCF generalized gradient (GGA) corrections for the exchange and the correlation energies (each for a few different functionals) are calculated and printed on output. The program can be instructed to use the GGA corrections in the potential during the SCF as well. This will in general have little effect on the formation energy, but it may affect the Density of States (DOS).