Calculation of DFT molecular properties using the q-Integral method

In this paper the accuracy of the q-Integral method is evaluated in several molecular properties of the H ₂ system using the Density Functional Theory (DFT). The q-Integral method is an alternative approach to evaluate two-electron integrals where the CPU time is substantially less than usual. For this purpose, we evaluated potential energy curves, rovibrational spectroscopy constants, rovibrational spectra, interatomic equilibrium distance and longitudinal static hyper (polarizability). All calculations were carried out through the STO-3G, STO-6G and double-ξ (DZV) atomic basis set. The results, using DFT methodology, are in good agreement with those obtained through the usual procedure of calculating the two-electron integrals, and show some of the same tendency as the previous results using HF, MP2 and Coupled Cluster methods. All calculations were performed in the general ab initio quantum chemistry package GAMESS, where we implemented the q-Integral method in the source code.