DZP basis set

During this process the atomic charges for the adsorbed molecules were taken from a Mulliken analysis of a DZP basis set Hartree Fock calculation (using CADPAC on the MOPAC (PM3) optimized molecular structure. Table 3 gives the cation charges for the sulfoxide group and C2 for each cation. In both cases the sulfur and transferred proton are positively charged but at sulfur the... 

The atomic basis consists in a double-zeta set expanded with polarization functions (DZP) and augmented by diffuse functions (DZPR). Exponents and contraction coefficient are from McLean and Chandler 1980 [18] diffuse functions, centered on the heavy atoms with exponents of 0.023 for the s orbitals and 0.021 for the p orbitals are from Dunning and Hay 1977 [34]. Extension of the DZP basis set with two sets of diffuse s (0.0437, 0.0184) and p (0.0399, 0.0168) functions (DZPRR) has also been tested. 

Tabfe 1. The Energy (AEst) Difference Between the X3Bi and a1 Ai States of Methylene (in kcal mol-1) Using Various Electronic Structure Methods and a DZP Basis Set. Taken from Ref. 36... 

Fig. 15.1 Comparison of Cl, MBPT and CC energies with respect to full Cl. The data set consists of the BH, HF and H20 molecules at bond distances of Re, 1.5 Re and 2.0 Re within a DZP basis set.

Table 2 Equilibrium bond lengths and dissociation energies for the F molecule with a DZP + basis set."...

The first set of MRCI calculations [89] was performed using the same DZP basis set as Grev and co-workers results are presented in Table 5.12, together with several single-reference results. 

Ab initio density functional theory calculations were also carried out on the CH2=XH(A) and CH(A)=XH2 series of molecules. The basis set used was the CEP-TZDP+ described previously26 and is more extensive than the DZP basis set used in the CAS(4,4)-OVB calculations. In TZDP+ the valence electron wave function is expanded in a triple-zeta sp set of functions plus a double set of polarization d-type functions plus a set of diffuse sp-type functions. The B3LYP exchange-correlation functional20 as defined in the Gaussian 94 program set35 was used in all the DFT calculations. 

Table 4 also contains an analogous analysis of the saturated CH3—XH3 systems for X = C - Pb, for comparison purposes. The optimized geometries were taken from CAS (2,2) calculations on CH3—XH3 using the CEP-DZP basis set. VBSCF calculations were then carried out on the CH3—XH3 set using the usual 3 VB structures one covalent (CH3 XH3) and two ionic (CII3 XI[3 and CH3-XH3+)39. 

Silyl radicals (1) are generally tetrahedral species. Deviation angles (y) have been calculated (UHF/DZP the DZP basis set is a double-zeta basis set with polarization functions) by Guerra to range from 13.4°[(H3Si)3Si ] to 22.7°[(PH2)3Si ]5. 

FCI energies of the ground state and several excited states (3 12+, 2 ll, and 2 2A states) were obtained by Olsen et al. [66] in 1989 using a DZP basis set augmented with diffuse functions. These data have been used as tests for a wide variety of EOM/FR-CC methods, including CCSD [20, 24], CCSDT-la [44], CC3 [45], CCSDT-3 [46], and CCSDt [52], Later Hirata et al. [49] obtained FCI results with the 6-31G basis set. Shiozaki et al. [57] have obtained FCI results with the augmented correlation-consistent polarized valence double-zeta (cc-pVDZ) and valence triple-zeta (aug-cc-pVTZ) sets. 

The results on tables 9 and 10 show that increasing the size of the cluster and/or the basis set does not change appreciably either the structure of the TS s or the activation energies obtained at a lower level of calculation (3T cluster and DZP basis set). Irrespective of the substrate and level of calculation employed, the results show that the protolytic cracking involves the attack of the zeolitic proton to a... 

Table 2.1 Electronic contributions to binding energies, -AE i, of H-bonds of type H3Z—HX, calculated using DZP basis set at SCF level. Data in kcal/moF.

Table 3.2 contains analogous information concerning the intensities of the various vibrational inodes. Comparison with the data in the last row illustrates the difficulty in computing experimental intensities to a high degree of accuracy. As in the ease of the frequencies, it appears that the DZP basis set seems to perform about as well as any of the much more extended sets in a number of instances. Deletion of the polarization functions leads to erratic fluctuations in the intensities, particularly the Vj symmetric stretching frequency of water. Minimal and 3-2IG are especially bad and should be avoided. Correlation does not influence the intensities in an obvious predictable manner. 

Similar sorts of conclusions apply to the frequencies. A systematic study " found that a DZP basis set yields vibrational frequencies within about 9% of experimental (harmonic) values. The discrepancy diminishes to 4% when correlation is included via CISD and to 2% with a coupled cluster treatment. Another set of calculations confirmed the eost-effec-tiveness of the MP2 treatment of vibrational frequencies, indicating better agreement with experiment than MP3 on some oceasions. Certain types of modes can be more sensitive to the level of theoretical treatment than others. For example, out-of-plane bending motions for it-bonded systems can require triple- plus two sets of polarization functions, as well as a set of/-functions in the basis set . 

Table 3.74 Frequency shifts and IR intensity enhancements of the two monomers in HCN—HCN complex. Data calculated at SCF level using DZP basis set .

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