  A new electronic structure model is developed in which the ground state
energy of a molecular system is given by a Hartree-Fock-like expression with
parametrized one- and two-electron integrals over an extended (minimal +
polarization) set of orthogonalized atom-centered basis functions, the
variational equations being solved formally within the minimal basis but the
effect of polarization functions being included in the spirit of second-order
perturbation theory. It is designed to yield good dipole polarizabilities and
improved intermolecular potentials with dispersion terms. The molecular
integrals include up to three-center one-electron and two-center two-electron
terms, all in simple analytical forms. A method to extract the effective
one-electron Hamiltonian of nonlocal-exchange Kohn-Sham theory from the
coupled-cluster one-electron density matrix is designed and used to get its
matrix representation in a molecule-intrinsic minimal basis as an input to the
paramtrization procedure -- making a direct link to the correlated wavefunction
theory. The model has been trained for 15 elements (H, Li--F, Na--Cl, 720
parameters) on a set of 5581 molecules (including ions, transition states, and
weakly-bound complexes) whose first- and second-order properties were computed
by the coupled-cluster theory as a reference, and a good agreement is seen. The
model looks promising for the study of large molecular systems, it is believed
to be an important step forward from the traditional semiempirical models
towards higher accuracy at nearly as low a computational cost.
