Slide 10 of 17
GVB calculations yield very accurate excitation energies, rotational barriers and bond energies. GVB-RCI is the simplest multideterminental reference wavefunction which properly dissociates to open shell fragments, regardless of the spin multiplicity of the fragments. Jaguar’s GVB-RCI employs a novel internal contraction scheme which restricts the number of CI coefficients in the RCI calculation to ~n3, where n is the number of GVB pairs. This scheme is shown to yield excellent agreement with the fully uncontracted CI.
Jaguar can also combine some of the strengths of GVB and DFT methods by performing GVB-DFT calculations, in which a GVB wavefunction is obtained self consistently, and the energy of the final, post-SCF wavefunction is done using the specified DFT functionals.
In all GVB calculations Jaguar automatically generates a highly refined initial wavefunction. The GVB treatment can be selectively applied to only the critical regions of a molecule (e.g., binding sites) by the specification of GVB pairs. Further RCI calculations can be carried out for some or all of the GVB pairs, thus incorporating the important correlation effects while keeping the overall computational cost down.