Analysis of parametric functionals in semiempirical approaches using simulation techniques

In this work a comparative study of energy functional components of a parametric Hamiltonian (H_pa) and those obtained from an analytical method is presented. Error cancellations in approximations occur between electronic and nuclear repulsion energies and between attractive and repulsive electronic components of the energy. Parametric functionals associated with the correlation energy are discussed. Some modifications to the studied H_pa, mainly in the way of simulating electron repulsion integrals, are tested. Simulation techniques based on binding energy functionals were utilized to parameterize the modified H_pa. Preliminary results indicate that important improvements of the total, electronic, and core–core repulsion energies with respect to analytical values can be obtained by modifying the way the electron repulsion integrals in H_pa are simulated.