Basis sets Ahlrichs type

Basis Hydrogen First row elements Second row elements  

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Table 5.2 Composition in terms of contracted and primitive basis functions for the Ahlrichs type basis sets...

Ahlrichs-type basis sets [88], simply by adding diffuse s and p functions with exponents obtained by dividing the smallest s and p exponent present by 3. This augmentation, used in combination with various density functionals, was found to be less important for the defZ than Pople-type basis sets but is important for reliable barrier heights and electron affinities. 

R. Ahlrichs, Theor. Chim. Acta, 33, 157 (1974). Methods for Efficient Evaluation of Integrals for Gaussian Type Basis Sets. 

The starting point is our previously performed calculations [3] using the Huzinaga basis set [20] (9s) for Be and (4s) for H, triple-zeta contracted, supplemented by the three 2p orbitals proposed for Be by Ahlrichs and Taylor [21] with exponents equal to 1.2, 0.3 and 0.05 respectively. This initial basis set, noted I, includes one s-type bond-function the exponent of which is equal to 0.5647. Several sets of diffuse orbitals have then been added to this basis I. Their corresponding exponents were determined by downward extrapolation from the valence basis set, using the Raffenetti [22] and Ahlrichs [21] procedure. Three supplementary basis sets noted II, III and IV containing respectively one, two and three... 

As said above it is possible to use the same Gaussian-type standard basis sets of ab initio theory for DFT calculations. Concerning the quality of the basis set which is necessary to obtain reliable results, it is advisable to use for Ge at least a split-valence basis set which should be augmented by a d-type polarization function such as 6-31G(d). Better basis sets of triple-zeta quality with more polarization functions up to 6-311G(3df) have been developed for Ge which belong to the standard basis sets in Gaussian 98. Other basis sets for Ge are available, e.g., from the compilations of Huzinaga et al. and Poitier et al. and from the work of Ahlrichs et al.. ... 

Ahlrichs who showed that an adjoined function should in general be constructed from two Gaussians. This is a probable reason why the adjoined basis sets of this type are not currently used. 

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