A NONLOCAL REPRESENTATION OF THE EFFECTIVE POTENTIAL DUE TO A MOLECULAR FRAGMENT

A non-local representation of the effective potential due to a molecular fragment is proposed here. Using this technique one can reproduce both Coulomb and exchange operators with kernels made up by molecular orbitals localized on a given molecular fragment. Such an approach seems particularly effective for large molecules with well-defined chemical fragments since in this case the kernel orbitals can be prepared through separate calculations on each fragment. The performance of the method is illustrated through calculations on specific molecular examples.