SCF level of theory

Table 4. The Relative Energies in kcal mol of the CH5 (Hj) structures (as Shown in Figure 4) at the TZ2P CISD+Q + ZPVE(TZ2P SCF) Level of Theory. (The Number of Imaginary Frequencies is in Squared Brackets)...

Manaa has considered the fullerene-like N60 molecule, and proposed that it could be formed from six bispentazoles (N10), or [N5+N5 ] salts under extreme conditions [73]. AMI and SCF levels of theory confirmed that N60 is a local minimum, and the reaction energy of N60 -> 6N,0 is estimated to exothermic by 2430 kcal/mol at the SCF level, indicating N60 would be a super-high-energetic molecule if synthesized. 

Figure 4. The system of coordinates and angular dependence of the interaction energy components in ArC02 at R=7.0 aQ A) at the SCF level of theory, B) at the correlated level of theory.

At the HF-SCF level of theory, the wave function is determined completely by the molecular orbitals. In the vast majority of cases, these are given by linear combinations of atom-centered basis functions, and these MO coefficients are obtained by the self-consistent field procedure. The first-order change to the wave function is therefore governed by the first-order change in the MO coefficients. It is not difficult to work out expressions for the derivatives of the MO coefficients,22 and one obtains... 

The results of Table 33.2 suggest that, as expected, the bulk of nonadditive interactions in the water trimer is reproduced quite well already at the SCF level of theory. This observation is further quantified in Fig. 33.2, where the three-body energies computed at the SCF and CCSD(T) levels are compared for ten trimers with maximum 0-0 separations less than 5 A extracted from a snapshot of a Monte Carlo (MC) simulation of liquid water at ambient conditions. Typically, trimers for which the nonadditive... 

In 1983, Pople et al. recalculated geometries of 14 and 15, using the unrestricted SCF level of theory in conjunction with the 6-31G basis set. They used the MP4SDQ/6-31G" method for single-point energy calculations. The results of their calculations for the triplet nitrene rearrangement were very similar to those in previous paper. 

The polarized basis set for S is [13 s.l0p.4d.4f/7 s.5p.2d.2f] Property values calculated according to Eq. 5.4 Values calculated according to Eqs. 5.3 and 5.5 Non-relativistic results calculated at the SCF level of theory, using the SCF optimized geometry Non-relativistic results calculated at the CCSD(T) level of theory... 

Non-relativistic results calculated at the SCF level of theory, using the SCF optimized geometry... 

The possibility to write down an (even if approximate) Hermitian Hamiltonian representing the sum of monoatomic and diatomic terms has a significant conceptual importance, in particular because the expectation values of these terms of the Hamiltonian reproduce the one- and two-center energy components in the CECA analysis [9], We hope that this way of writing the Hamiltonian will permit to accomphsh some a priori approaches to molecular structure problems, and not only a posteriori ones like the energy decomposition. In the next section, we shall consider the application of our approach at the SCF level of theory it is not utilizing explicitly the detailed form (32)-(34) of the Hamiltonian. 

Triplet states of 16. The A2 state can be pictured as a cycloheptatrienyl radical, whereas the B state resembles a pentadienyl radical, whose terminal atoms interact only weakly with the connecting C-C double bond. In 16 the a electron cannot interchange with the n system at SCF levels of theory (UHF and ROHF) and one finds both states to be minima. Inclusion of dynamic electron correlation increases the energy gap between the two triplet states and the B state is a saddle point at MP2 and BLYP. This situation is reversed at the CASSCF level, where Bi, now a minimum, is only 2-3 kcal mol below the A2 state (transition structure), Following the imaginary mode of A2-16 leads, via intermediate geometries of Cs symmetry, to the Bj state, quite similar to the situation found in the cycloheptatrienyl radical. 

The contribution of the Fermi contact term to J(NN) in both trans- and C/S-N2H2 was computed using the scanning molecular orbital method, a special approach within the Har-tree-Fock framework [4]. The diamagnetic spin-orbital (DSO) contribution to J(HH) in N2H2 was calculated at the ab initio SCF level of theory [5]. 

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