Single-reference configuration interaction

To check the influence of correlation energy on the analysis performed, single reference configuration interaction calculations [hereafter referred to as Single plus Double Configuration Interaction (SDCI)] have been carried out on the compound Fe CO)i 7i -CH2O), by using the direct-CI method [3]. 58 electrons have been frozen because of the dimensions... 

CISD single-reference configuration interaction with single and double replacements... 

Figure 1. The shape of the potential curve for nitrogen in a correlation-consistent polarized double-zeta basis set is presented for the variational 2-RDM method as well as (a) single-reference coupled cluster, (b) multireference second-order perturbation theory (MRPT) and single-double configuration interaction (MRCl), and full configuration interaction (FCl) wavefunction methods. The symbol 2-RDM indicates that the potential curve was shifted by the difference between the 2-RDM and CCSD(T) energies at equilibrium.

Structures were optimized at the theoretical level described in Table 1, footnote a. Final energies were obtained by using multi-reference configuration interaction (MRCI) wave functions including single and double excitations from die reference wave functions. cFrom Reference 8. 

MRCIS, single excitation multi-reference configuration interaction ... 

Multi-Reference Configuration Interaction (MRCI) calculations were subsequently performed on the saddle point, the reagents, and the products, in order to improve the determination of the barrier height and the exoergicity. These calculations, which include single and double excitations from the active orbitals, have been performed by using the direct-CI method [10]. Davidson s correction [11] was also added to account for the effect of unlinked clusters this will be denoted MRCI-I-Q in Table 1. 

As explained above, the dynamic electronic correlation can be taken into account by the (truncated) configuration interaction method in the case of a single reference system. Similarly, the multi-reference configuration interaction (MRCI) method can be used for multi-reference systems. In this method, a CASSCF wavefunction is used as the zeroth order description of the system. A configuration interaction matrix... 

---