Dunning double zeta contracted basis

Dunning-type contractions are characterized by considerable flexibility in the valence part of the primitive space. Typically, the outermost primitive functions are not contracted at all, contraction being reserved for the inner parts of the valence orbitals and the core orbitals. The commonest contracted set of this type is probably the [4s 2p] contraction of the (9s 5p) set. Unfortunately, there are at least two such double zeta contraction schemes in use, as well as an erroneous one. Some care may be required to reproduce results asserted to be obtained with a Huzinaga-Dunning [4s 2p] basis . Because of the relatively flexible contraction scheme these basis sets usually perform well, especially when large primitive sets such as van Duijneveldt s (13s 8p) sets are used. However, it should be noted that such primitive sets are difficult to contract this way without significant loss of accuracy at the atomic SCF level, unless very large contracted sets are used. 

Of the Dunning-Huzinaga basis sets, the [4s2 p set has been particularly popular. This double-zeta (DZ) basis set, in which there are two contracted functions for each occupied AO, represents... 

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. 

The double zeta basis sets, such as the Dunning-Huzinaga basis set (D95), form all molecular orbitals from linear combinations of two sizes of functions for each atomic orbital. Similarly, triple split valence basis sets, like 6-3IIG, use three sizes of contracted functions for each orbital-type. 

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. 

F + Ha->FH + H.—Bender et al.26S recently reported the results of two different sets of calculations on the potential energy surface for the reaction F + H2-+ FH + H. This work is of interest from three points of view. First, it is truly a rigorous quantum mechanical calculation typifying the current state of the art for systems of this size a GTO basis set of double-zeta quality is used (9s5pj4s) for a total of 32 GTO s, and this is contracted according to the Dunning method51 to... 

The first set of calculations (Figure 2.1) was done using Dunning s contracted correlation-consistent basis set of double-zeta quality augmented with a set of diffuse functions, aug-cc-pVDZ (10s5p2d) [4s3p2d]. Each PEC was obtained from 30-35 calculated points. 

---