22 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.

RKS or RKS-SCF

calls the spin-restricted Kohn-Sham program. KS and KS-SCF are aliases for RKS.

UKS or UKS-SCF

calls the spin-unrestricted Kohn-Sham program

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

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

If no functional keyname is given, the default is LDA (see below). Following this command may appear directives specifying options for the density-functional modules (see section 18.2) or the Hartree-Fock program (see section 17.1).

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.

Normally, sensible defaults are used to define the integration grid. The accuracy can be controlled using options as described in section 18.1 or directives as described in section 18.2). More control is provided by the GRID command, as described in section 18.3.