18 THE DENSITY FUNCTIONAL PROGRAM

Density-functional theory calculations may be performed using one of the following commands:

DFT

calculate functional of a previously computed density.

KS or KS-SCF

calls the closed-shell self-consistent Kohn-Sham program

RKS or RKS-SCF

calls the spin-restricted open-shell Kohn-Sham program

UKS or UKS-SCF

calls the spin-unrestricted open-shell Kohn-Sham program

Each of these commands may be qualified with the key-names of the functional(s) which are to be used:

command, key1, key2, key3, $\ldots$

If no functional keyname is given, the contents of the MOLPRO vector variable DF is interpreted as a list of functionals; If DF is empty, DFTNAME is examined; otherwise, the default is LDA (see below). Following this command may appear commands specifying options for the density-functional code, followed, in the Kohn-Sham case, by further SCF options exactly as for the Hartree-Fock programs.

On completion of the functional evaluation, or self-consistent Kohn-Sham calculation, the values of the individual functionals are stored in the MOLPRO vector variable DFTFUNS; the total is in DFTFUN, and the corresponding individual functional names in DFTNAME.

Energy gradients are available for self-consistent Kohn-Sham calculations.