Kohn-Sham energies are calculated by diagonalization of the Kohn-Sham matrix for a given potential. The potential is specified by a set of orbitals and occupation numbers. The diagonalization for the lowest eigenstates is performed with a variation of the iterative Davidson method [32]. As this option can be used in a seperat run as well as in connection with another runtype (e.g. Wavefunction Optimization) some confusion about restart files and restart options exists. Special care is necessary to avoid the use of ionic corrdinates that do not correspond to the electronic potential.
If the Kohn-Sham energies option is used in a seperate run, the wavefunctions (defining the potential) are read from the file RESTART and the coordinates are read from the input file. If also the coordinates should be read from the RESTART file one has to specify the keyword RESTART COORDINATES. A specification of RESTART WAVEFUNCTIONS is interpreted as a restart of a diagonalization run, i.e. the wavefunctions (occupied and virtual) are read from the file KSORB and the potential is build from these wavefunctions. In the case when the occupied states are not converged to self-consistency unfortunately the potential is changed w.r.t. the last run. If Kohn-Sham energies is used in connection with another runtype the wavefunctions and coordinates are always read from the restart file specified in LATEST.
At the end of a run two files are written. The file KSORB containes all requested eigenstates (converged or not) of the Kohn-Sham matrix and the file RESTART.x is a standart restart file with the occupied KS-eigenstates.