Basis sets Dunning-Huzinaga

McLean and Chandler developed a similar set of contracted basis sets from 

Huzinaga s primitive optimized set for second row elements.A DZ type basis is derived by contracting (12s8p) — [5s3p], and a TZ type is derived by contracting (13s9p) — [6s4p]. The latter contraction is 6,3,1,1,1,1 for the s-functions and 4,2,1,1,1 for the p-functions, and is often used in connection with the Pople 6-3IG when second 

The Dunning-Huzinaga type basis sets do not have the restriction of the Pople style basis-sets of equal exponents for the s- and p-functions, and they are therefore somewhat 

The primary reason for the popularity of the Pople and DH style basis sets is the -extensive calibration available. There have been so many calculations reported with these basis sets that it is possible to get a fairly good idea of the level of accuracy that can be attained with a given basis. This is of course a self-sustaining procedure, the more calculations that are reported with a given basis, the more popular it becomes, since the calibration set becomes larger and larger. 

The Dunning-Huzinaga type basis sets do not have the restriction of the Pople style basis sets of equal exponents for the s- and p-functions, and they are therefore somewhat more flexible, but computationally also more expensive. The major determining factor, however, is the number of basis functions and less so the exact description of each function. Normally there is little difference in the performance between different DZ or different TZ type basis sets. 

The primary reason for the popularity of the Pople and DH style basis sets is the extensive calibration available. There have been so many calculations reported with these basis sets that it is possible to get a fairly good idea of the level of accuracy that 

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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. 

Before leaving this topic, it should be mentioned that, in addition to the (Pople) basis sets discussed so far, there are others as well. The more popular ones include the Dunning-Huzinaga basis sets, correlation consistent basis sets, etc. These functions will not be described here. 

Modified NDDO Models 85 r 5.4.2 Dunning-Huzinaga Basis Sets 160... 

Doubles, doubly excited configurations, 100 Douglas-Kroll transformation, 215 DREIDING force field, 40 Dummy atom, 37, 417 Dunning-Huzinaga basis sets, 160 Dynamic properties, 235 Dynamical electron correlation, 118... 

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... 

For the qualitative analysis of basis set effects in the CH systems (e.g, CH ), we used Huzinaga-Dunning triple-( basis sets, —designated C(1056p/553/ ) and H(55/35)—with two sets of polarization functions (TZ2P) on all the nuclei. The polarization function exponents were a C) = 1.50, 0.375. The... 

Many basis sets are just identihed by the author s surname and the number of primitive functions. Some examples of this are the Huzinaga, Dunning, and Duijneveldt basis sets. For example, D95 and D95V are basis sets created by Dunning with nine s primitives and hve p primitives. The V implies one particular contraction scheme for the valence orbitals. Another example would be a basis set listed as Duijneveldt 13s8p . 

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. 

Up to now we have assumed that each primitive function is used in the contraction only once, i.e. each primitive function is only involved in one particular contracted function. The contractions of this type are referred to as segmented. In some cases it may occur that for a given primitive set the Dunning s rules suggest a higher number of CGTF s than we intended for a molecular calculation. Con-aider for example the (9s) and (lOs) basis sets of Huzinaga for the first-row atoms. The former contracts satisfactorily to a C4s] set,... 

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