VALENCE BASIS-SETS FOR TELLURIUM - WEIGHT-FUNCTIONS AS A BASIS-SET DEVELOPMENT TOOL AND INITIAL MOLECULAR APPLICATIONS

Pseudopotentials are a reliable ab initio method for treating large mo lecules containing heavier elements. To improve the valence basis sets used along with these pseudopoentials, we present a simple procedure to modify such basis functions based on an analysis of the associated weight functions. Tellurium was chosen as a specific test element and a basis set prepared to complement a relativistic core pseudopotential . Valence basis sets to be combined with core electron pseudopotential s were also developed for the elements Se, S, N, O, C and F. Tests wer e performed and the results compared to predictions using other basis sets. The basis sets thus constructed give generally good agreement wi th experiment and with results using established basis sets. The resul ts for the C-2v and D-3h forms of the X(3) molecules (X = S, Se, Te) w ith the new basis sets and using second order Moller-Plesset perturbat ion theory are comparable to those using other basis sets and the mult i configurational self-consistent field approach.