VCI calculations account for vibration correlation effects and are based on potential
energy surface as generated from the SURF program) and a basis of VSCF modals.
All VCI calculations will be performed state-specific, i.e. for each vibrational mode an individual
VCI calculation will be performed. As VCI calculations may require substantial computer resources, these
calculations can be rather expensive.
Currently, two different VCI programs (configuration selective and conventional) are available (see below).
Moreover, VCI calculations can be performed using the grid-based version of the program or within
a polynomial representation. The latter is significantly faster and is thus recommended.
The different versions of the
configuration selection VCI program and the underlying configuration selection scheme are described in
detail in:
M. Neff, G. Rauhut, Toward large scale vibrational configuration interaction calculations,
J. Chem. Phys. 131, 124129 (2009).