We introduce a hybrid Gaussian charge distribution model (HGM) that partitions the molecular electron density into overlapping
spherical atomic domains. The semi-empirical HGM consists of atom-centered spherical Gaussian functions and discrete point charges,
which are optimized to reproduce the electrostatic potential on the molecular surface as well as the number of electrons in
atom-centered and certain off-atom-centered spherical regions as closely as possible. In contrast, our previous Gaussian charge
distribution model [J. Chem. Phys. 129, 014509 (2008)] contained only spherical Gaussian functions and was not required to
reproduce the number of electrons in off-atom-centered regions. Variable van der Waals (vdW) radii fluctuating around the Bondi radii
are derived from the HGM based on the isodensity contour concept and further employed to define the molecular cavity in our quantum
mechanical/Poisson–Boltzmann/surface area model as well as the polarizable continuum model. The variable vdW radii produce more
accurate solvation free energies for 31 neutral molecules than the Bondi radii for both continuum solvent models (CSM)
consistently. Moreover, for H atoms, the linear dependence of the atomic radii on the atomic partial charges is identified.
Founded in 1887, the Zeitschrift für Physikalische Chemie covers the main developments in physical chemistry, placing with an emphasis on experimental research. It represents a combination ofdiscusses reaction kinetics and spectroscopy, surface research and electrochemistry, thermodynamics and the structure analysis of matter in its various conditions, among other topics.