Calculation of nonlinear optical susceptibilities of pure liquids within the Polarizable Continuum Model; the effect of the macroscopic nonlinear polarization at the output frequency

We present an extension of the Polarizable Continuum Model to compute nonlinear optical (NLO) macroscopic susceptibilities of pure liquids. The procedure is based on the interpretation of the molar property (i.e. the macroscopic susceptibilities) in terms of effective molecular dipoles and (hyper)polarizabilities for a system immersed in the surrounding medium, represented by a continuum dielectric. The effective quantities are obtained through an ab initio description of the molecule under scrutiny interacting with the macroscopic field at the fundamental frequency and with the nonlinear macroscopic polarization at the output frequency.