CCSD calculations geometries

SOPPA(CCSD) calculations with the CCSD or MCSCF PEC are also larger. In general the differences in the ZPVC are larger between the different PEC than between the different linear response methods. The SOPPA(CCSD) results for the equilibrium geometry as well as the vibrationally averaged polarizabilities are in both molecules in better agreement with the MCSCF results than the pure SOPPA values. 

The potentially aromatic silabenzenoids, s-l,3,5-trisilatriazine (41)68 and 2-, 3- and 4-silapyridines (42-44)69, were studied by Veszpremi and coworkers. The MP2/6-31G calculated geometries of 41-44 are given in Figure 7 (almost identical geometries were calculated for 41 also at MP2/6-311G and CCSD/6-31G 68). 41 has D3h symmetry... 

FIGURE 38. Calculated geometries (at CCSD/TZ2P for M = Si497 and CCSD/TZP+f for M = Ge494) of the side-on complex of MH5 1 (124). Bond lengths in pm... 

FIGURE 32. Calculated geometries at MP2 and transition metal (TM)—Ge bond dissociation energies De [at CCSD(T)] of the CITM complexes (TM = Cu, Ag, Au) with the ligand germaimidazol-2-yhdene. Bond distances are in A, angles in deg. Reprinted with permission from Reference 145. Copyright 1998 American Chemical Society... 

Scheme 1-5 The Bergman reaction. Calculated geometries (CCSD(T)/6-31G(d,p)) are taken from [116e]. Bond lengths in A, bond angles in degrees.

The S-T splitting is obtained as a difference of the two separate individual energy calculations for the singlet and triplet. Those individual singlet and triplet calculations do not necessarily have to be by the same method, and in fact, the majority of the results in Table 1 use composite methods in which the singlet and triplet are treated by two different methods (primarily the singlet as a MR state while the triplet is SR). RMR indicates the reduced multi-reference approach of Li and Paldus [58]. The TD-CCSD of Baikova and Bartlett [54], an early SU-CCSD application, provides two roots simultaneously at each geometry. This SU-CCSD calculation introduced GVB CCSD as a two-determinant reference. The MR-BW is a state-specific MR... 

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