Optimizatrw of software package for studies of quantum nuclear effects: Apmo

This paper describes the optimization of the overall calculation scheme and the implementations of an efficient system for calculate molecular integrals in the APMO software package (Any Particle Molecular Orbital). APMO is an implementation of the nuclear and electronic molecular orbital (NEMO) method at Ha-tree-Fock (HF) and MP2 levels of theory. In this method, both nuclei and electrons are represented as wave functions, which allow the study of phenomena where nuclear quantum effects are important, such as isotope effects, hydrogen bonding, proton transfer, and others. This optimization reached a marked decrease in global and molecular integrals calculation times and enabled the use of basis functions with angular momenta higher than d and allowed the calculation of systems with more than eight atoms. This paper also presents the application of the NEMO method to the study of the isotope effect on mono and di hydrated complexes of copper (I) and zinc (II). For these systems, we found that the substitution of a proton with a deuteron nucleus weakens the metal-oxygen bond.