Basis sets Locally dense

It is also important that sufficiently large basis sets are used. The 6—31G(d) basis set should be considered the absolute minimum for reliable results. Some studies have used locally dense basis sets, which have a larger basis on the atom of interest and a smaller basis on the other atoms. In general, this results in only minimal improvement since the spectra are due to interaction between atoms, rather than the electron density around one atom. 

On the Usage of Locally Dense Basis Sets in the Calculation of NMR Indirect Nuclear Spin-Spin Coupling Constants Vicinal Fluorine-Fluorine Couplings... 

Fig. 1. Dependence of the vicinal F-F coupling constant in difluoroethyne on the basis set used for the carbon atoms Deviation (in Hz) of the locally dense basis set result from the calculation with the apTJ/apTJ basis set. Only the basis sets on the non-coupled atoms are used as labels on the basis set axis. The apTJ basis set was used for fluorine in all calculations.

Table 4. Errors in the vicinal F-F coupling constants and reduction in the number of basis functions for various locally dense basis sets in comparison with the apTJ/apTJ/apTJ basis set for difluoroethyne (1) and the 1,2-difluoroaIkanes, (2) and (4), and the apTJ/apTJ/pT basis set for the 1,2-difluoroalkanes, (6) and (8). All calculations were carried out using SOPPA...

M. Sanchez, P.F. Provasi, G.A. Aucar, S.P.A. Sauer, On the usage of locally dense basis sets in the calculation of NMR indirect nuclear spin-spin coupHng constants vicinal fluorine-fluorine coupHngs, Adv. Quant. Chem. 48 (2005) 161. 

De Dios, Pearson, and Oldfield make one other approximation that has proven useful in shielding calculations on large systems by employing what we have called locally dense basis sets and what Huber - (in applications to the calculation of quadrupole coupling constants) has described as... 

D. B. Chesnut and K. D. Moore, J. Comput. Chem., 10,648 (1989). Locally Dense Basis Sets for Chemical Shift Calculations. 

Use of Locally Dense Basis Sets for Nuclear Magnetic Resonance Shielding Calculations. 

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