#! /bin/sh # The computation of multiplet states corresponding to an open-shell system can # be carried out with ADF by first computing the 'Average-of-Configuration' # (aoc) state, where all orbitals in the open shell are degenerate and equally # occupied. This computation is spin-restricted and serves as a fragment file # for the multiplet run, where then different occupation numbers are assigned to # the various orbitals in the open shell. The corresponding energies are # computed in the field of the aoc, which is achieved by not iterating the self- # consistency equations to convergence but only computing the orbitals in the # initial field. # Since ADF requires that all symmetry-partners in an irreducible representation # (irrep) have equal occupations, the multiplet calculation, where such orbitals # are not equally occupied, must be carried out in a formally lower point group # symmetry. The point group to select and the appropriate occupation numbers to # apply must be worked out by the user 'on paper' in advance. # See the discussion of Multiplet energies in ADF manual. # The script starts with the 'creation' of the required basic atoms, N, H, Cr # using a fair basis set quality. # The next step is the computation of the ammonia fragment NH3. This is not a # crucial step here: the multiplet state computation can equally well be carried # out by not using any intermediate compound fragments. However, it illustrates # once more how a bigger molecule can be built up from smaller, but not trivial # fragments. $AMSBIN/dirac -n1 < $AMSRESOURCES/Dirac/Cr.2p mv TAPE12 t12.rel AMS_JOBNAME=Cr $AMSBIN/ams <