Ab initio study of high tridymite by the formalism generator coordinate Hartree-Fock

The Generator Coordinate Hartree-Fock (GCHF) Method is applied to generate extended 14s 8p and 17s 11p Gaussian basis sets for the atoms O and Si, res pectively. The role of the weight functions in the assessment of the numeri cal integration range of the GCHF is shown. The Gaussian basis sets are con tracted to [6s4p] O atom and [8s5p] Si atom by the Dunning's segmented cont raction scheme. To evaluate the quality of our contracted [6s4p] and [8s5p] bases in molecular calculations we accomplish calculations of total and or bital energies in the Hartree-Fock-Roothaan method for O-2 and SiO molecule s. We compare the results obtained with the our (14s 8p) and (17s 11p) base s sets with the of 6-311G basis and with values from the literature. The ad dition of one d polarization function in the silicon basis and its utilizat ion with the basis for oxygen leads to the calculation of electronic proper ties and IR Spectrum of high tridymite in space group D-3d. (C) 1999 Elsevi er Science B.V. All rights reserved.