Contracted basis sets kinetic balance

When it comes to contracted basis sets, kinetic balance strictly applied to the contracted large component can lead to problems. While it would be possible to apply the kinetic balance relation to derive a small-component basis from a set of large-component contracted basis functions, this procedure has been shown to be unsuitable in practice (Visscher et al. 1991). The best approach for generating contracted basis sets for relativistic four-component calculations has been to start with an uncontracted large-component basis, and to construct a small-component basis from this basis using kinetic balance. This set is then used in an uncontracted DHF calculation for the atom in question, yielding large- and small-component atomic functions that are kinetically... 

One final point which should be mentioned in connection with the kinetic balance requirement concerns the use of contracted basis functions. In a contracted basis set the basis functions used for expansion of the variational problem are themselves fixed linear combinations of the primitive basis functions... 

L. Visscher, P. J. C. Aerts, O. Visser, W. C. Nieuwpoort. Kinetic Balance in Contracted Basis Sets for Relativistic Calculations. Int. J. Quantum Chem., Quantum Chem. Symp., 25 (1991) 131-139. 

Visscher, L., Aerts, P.J.C., Visser, O., Nieuwpoort, W.C. Kinetic balance in contracted basis sets for relativistic calculations. Int. J. Quant. Chem. 40, 131-139 (1991)... 

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