Theoret. Chem. Acc. manuscript No. (will be inserted by the editor) Local Random Phase Approximation with Projected Oscillator Orbitals

Abstract An approximation to the many-body London dis-persion energy in molecular systems is expressed as a func-tional of the occupied orbitals only. The method is based on the local-RPA theory. The occupied orbitals are local-ized molecular orbitals and the virtual space is described by projected oscillator orbitals, i.e. functions obtained by multiplying occupied localized orbitals with solid spheri-cal harmonic polynomials having their origin at the orbital centroids. Since we are interested in the long-range part of the correlation energy, responsible for dispersion forces, the electron repulsion is approximated by its multipolar expan-sion. This procedure leads to a fully non-empirical long-range correlation energy expression. Molecular dispersion coefficients calculated from determinant wave functions ob-tained by a range-separated hybrid method reproduce exper-imental values with less than 15 % error