Optimization and transferability of non-electrostatic repulsion in the polarizable density embedding model.

Embedding techniques in combination with response theory represent a successful approach to calculate molecular properties and excited states in large molecular systems such as solutions and proteins. Recently, the polarizable embedding model has been extended by introducing explicit electronic densities of the molecules in the nearest environment, resulting in the polarizable density embedding (PDE) model. This improvement provides a better description of the intermolecular interactions at short distances. However, the electronic densities of the environment molecules are calculated in isolation, which results in overestimation of the non-electrostatic repulsion, thereby requiring a scaling of this term. In this work, an optimal scaling factor for the non-electrostatic repulsion term is examined by comparing intermolecular interaction energies obtained with embedding techniques to reference interaction energies calculated on the basis of full quantum-mechanical calculations. The obtained optimal factors are used in PDE calculations of various ground- and excited-state properties of molecules embedded in solvents described as polarizable environments. © 2017 Wiley Periodicals, Inc.