Coupled-cluster theory potential energy curves

Figure 4. Ground-state potential energy curves of Hs from 2-RDM and wavefunction methods are shown. MP2 and MP4 denote second- and fourth-order perturbation theories, while CCSD and CCSD) represent coupled cluster methods.

Fig. 7. Distance-dependent potential energy curves for the anunonia adduct to the silyl cation, H3N"-SiH3 at different levels of correlated wavefunctions density functional theory (DFT-B3LYP) with a basis set of triple-zeta quality (aug-cc-pVTZ), MP2 as well as MP4 perturbation, and coupled cluster CCSD(T) calculations with double-zeta basis sets (aug-cc-pVDZ).

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.

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