Comparison of the Marcus and Pekar partitions in the context of non-equilibrium, polarizable-continuum solvation models

• Published in: The Journal of chemical physics 2015-11, Vol.143 (20), p.204104-204104
• Main Authors: You, Zhi-Qiang, Mewes, Jan-Michael, Dreuw, Andreas, Herbert, John M
• Format: Article
• Language: English
• Subjects: Chemical partition; COMPARATIVE EVALUATIONS; Computational chemistry; Conductors; Continuum modeling; CORRECTIONS; DIELECTRIC MATERIALS; Dielectric polarization; EQUILIBRIUM; Equivalence; EV RANGE; EXCITATION; Formulations; FREE ENERGY; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INTEGRAL EQUATIONS; INTERCHANGEABILITY; Ionization; Mathematical models; MOLECULES; PARTITION; Partitions; PERTURBATION THEORY; Physics; POLARIZATION; QUANTUM MECHANICS; SOLUTES; SOLUTIONS; SOLVATION; SOLVENTS
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.4936357

The Marcus and Pekar partitions are common, alternative models to describe the non-equilibrium dielectric polarization response that accompanies instantaneous perturbation of a solute embedded in a dielectric continuum. Examples of such a perturbation include vertical electronic excitation and vertical ionization of a solution-phase molecule. Here, we provide a general derivation of the accompanying polarization response, for a quantum-mechanical solute described within the framework of a polarizable continuum model (PCM) of electrostatic solvation. Although the non-equilibrium free energy is formally equivalent within the two partitions, albeit partitioned differently into "fast" versus "slow" polarization contributions, discretization of the PCM integral equations fails to preserve certain symmetries contained in these equations (except in the case of the conductor-like models or when the solute cavity is spherical), leading to alternative, non-equivalent matrix equations. Unlike the total equilibrium solvation energy, however, which can differ dramatically between different formulations, we demonstrate that the equivalence of the Marcus and Pekar partitions for the non-equilibrium solvation correction is preserved to high accuracy. Differences in vertical excitation and ionization energies are