Integrated Multiscale Multilevel Approach to Open Shell Molecular Systems

We present a novel multiscale approach to study the electronic structure of open shell molecular systems embedded in an external environment. The method is based on the coupling of multilevel Hartree-Fock (MLHF) and Density Functional Theory (MLDFT), suitably extended to the unrestricted formalism, to Molecular Mechanics (MM) force fields (FF). Within the ML region, the system is divided into active and inactive parts, thus describing the most relevant interactions (electrostatic, polarization, and Pauli repulsion) at the quantum level. The surrounding MM part, which is formulated in terms of nonpolarizable or polarizable FFs, permits a physically consistent treatment of long-range electrostatics and polarization effects. The approach is extended to the calculation of hyperfine coupling constants and applied to selected nitroxyl radicals in an aqueous solution.

Automated summary

This paper presents a new multiscale approach for studying the electronic structure of open shell molecular systems in an external environment. The method involves coupling multilevel Hartree-Fock and Density Functional Theory with Molecular Mechanics force fields. The system is divided into active and inactive parts, describing relevant interactions at the quantum level, while the surrounding Molecular Mechanics part allows for a consistent treatment of long-range electrostatic and polarization effects. The approach is also extended to the calculation of hyperfine coupling constants and applied to selected nitroxyl radicals in an aqueous solution.