Self-consistency

The SCF procedure searches for a self-consistent density. The self-consistent error is the square root of the integral of the squared difference between the input and output density of the cycle operator. When the SCF error is below a certain criterion, controlled by CONV, convergence is reached. In case of bad convergence the SCF search can be controlled by the DIIS block, of which the most interesting entry is POTENTIAL, implying that the DIIS scheme is applied to the potential, rather than the density.