  Nonlinear optical properties (NLOPs) play a major role in photonics,
electro-optics and optoelectronics, and other fields of modern optics. The
design of new NLO molecules and materials has benefited from the development of
computational tools to analyze the relationship between the electronic
structure of molecules and its optical response. In this paper, we present a
new means to analyze the response property through the partition of NLOPs in
terms of orbital contributions (PNOC). This tool can be used to obtain a local
representation of the NLOPs, providing a powerful visualization aid to connect
the magnitude of the optical property with some parts of the molecule. Unlike
other methods to analyze NLOPs, the PNOC decomposes the optical property into
orbitals of the unperturbed system, furnishing this method with the ability to
assess the performance of single- and multi-determinant electronic structure
methods. PNOC can be also used to design small basis sets for an accurate
description of large systems, saving a substantial amount of computer time for
the calculation of optical properties.
