Dunning-Hay basis

Table 14.2 CO coie-exdtation energies by ASCF using DFT/cc-pCVK with the Dunning-Hay basis functions in eV...

An older, but still used, notation specihes how many contractions are present. For example, the acronym TZV stands for triple-zeta valence, meaning that there are three valence contractions, such as in a 6—311G basis. The acronyms SZ and DZ stand for single zeta and double zeta, respectively. A P in this notation indicates the use of polarization functions. Since this notation has been used for describing a number of basis sets, the name of the set creator is usually included in the basis set name (i.e., Ahlrichs VDZ). If the author s name is not included, either the Dunning-Hay set is implied or the set that came with the software package being used is implied. 

Dunning-Hay double-zeta basis sets [25], augmented by one polarization function for each atom (p for hydrogen, d for everything else), were used for all calculations. 

The ab initio search for adequate basis functions, after a decade, showed that the failure of the atomic orbital basis comes from the change in size and shape of the atomic orbitals in the high electrostatic fields of the other atoms. Use of a double-zeta plus polarization basis, such as the Dunning-Hay split-valence or one of the Pople x-yzG bases, allows flexibility for the atomic orbitals to adjust to the molecular environment. 

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. 

Dunning TH Jr, Hay PJ (1976), Gaussian Basis Sets for Molecular Calculations. In Schaefer HF III, (ed) Modem Theoretical Chemistry, vol. 3, Plenum, New York, pp 1-27... 

Dunning, T.H. and Hay P.J., Gaussian basis sets for molecular calculations, in Methods in Electronic Structure Theory, H.F. Schaefer III, Editor. 1977, Plenum New York. p. 1-27. 

Dunning TH, Jr, Hay PJ (1977) Gaussian basis sets for molecular calculations. In Schaefer III HF (ed) Modern theoretical chemistry. Methods of electronic structure theory, vol 3, Chap 1. Plenum Press, NY, pp 1-30... 

In order to test the general validity of the previous results, first we have applied algorithm MC-A to a set of diatomic systems, shown in Table VII. In all the cases, we have used SCF MO s as starting point. The "split valence" basis set of Dunning and Hay /51 / was used for each atom and the interatomic distances were taken from the work of Snyder and Basch /52/ or, if not quoted there, as the experimental reported value. Almost quadratic convergence is obtained in all cases. The number of MO iterations needed in each global iteration varies with the number of orbitals present, as expected. Furthermore, we have also verified the invariance of the final result from the starting point. 

All calculations employed extended basis sets constructed from contracted Gaussian type orbitals. Basis sets were, in general, taken from the work of Huzlnaga (26) and Dunning and Hay (27). 

Owing to computational limitations, the model used to represent the first shell of CA was the (NH3)3M (H20) system. This complex has been widely used in ab initio calculations of different mechanistic aspects of the CA enzyme [31]. Furthermore, the validity of this model, where the three imidazole ligands are substituted by three ammonia groups, has been previously assessed [31e, 32]. In the present study, full geometry optimizations of all eight minima with no symmetry constraints were performed. Pseudopotential wave functions have been preferred to full-electron calculations, because valence Similarity can be more easily related to reactivity than all-electron Similarity [33]. Dunning s valence double zeta quality basis set [34] together with the Hay and Wadt ECPs... 

Dunning T H Jr and Hay P J 1977 Gaussian basis sets for mclecular calculations Methods of Electronio Struoture Theory vo 3, ed H F III Schaefer (New York Plenum) pp 1-27... 

Ermler-Christiansen EGP and basis set with/-type polarizing functions [5s5p4dlf] for Mo and W, Hay-WadtECP and basis set with additional diffuse functions for S, Dunning s TZVP basis with additional diffuse functions for O and N, as well as for C and H in the substrate, and Dunning s D95 basis set for C and H in other groups. 

Calculations were carried out with the GAUSSIAN 98 program [10]. Geometries of the structures were optimized with the B3LYP functional. Harmonic vibration frequencies were calculated for each structure. LANL2DZ basis set (the Hay-Wadt effective core potential [11] plus double-zeta basis for molybdenum and aluminium atoms, Dunning-Huzinaga valence double-zeta basis set for other elements) was employed. 

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