Self-consistent continuum solvation (SCCS): The case of charged systems

Abstract

The recently developed self-consistent continuum solvation model (SCCS) [O. Andreussi, I. Dabo, and N. Marzari, J. Chem. Phys. 136, 064102 (2012)] is applied here to charged species in aqueous solutions. Describing ions in solution represents a great challenge because of the large electrostatic interactions between the solute and the solvent. The SCCS model is tested over 106 monocharged species, both cations and anions, and we demonstrate its flexibility, notwithstanding its much reduced set of parameters, to describe charged species in solution. Remarkably low mean absolute errors are obtained with values of 2.27 and 5.54 kcal/mol for cations and anions, respectively. These results are comparable or better than the state of the art to describe solvation of charged species in water. Finally, differences of behavior between cations and anions are discussed.

Methods of photoelectrode characterization with high spatial and temporal resolution

“…This approach has long been used in the quantum chemistry community to study ionic and molecular solvation, 227 and similar ideas are now beginning to be adapted for solid-liquid interfaces. [228][229][230][231][232] Such polarizable continuum-based schemes can also mitigate another critical challenge for realistic simulations of electrode-electrolyte interfaces and catalytic redox electrochemistry-namely, the application of a well-defined voltage bias or photo-bias. Typically, there are two complications associated with an external bias within DFT: first, charge neutrality considerations that prevent accurate determination of a potential reference for a charged system that can be directly compared with experiments; and second, fundamental incompatibilities with the periodic boundary conditions generally employed for simulations of extended crystalline systems.…”

“…Typically, there are two complications associated with an external bias within DFT: first, charge neutrality considerations that prevent accurate determination of a potential reference for a charged system that can be directly compared with experiments; and second, fundamental incompatibilities with the periodic boundary conditions generally employed for simulations of extended crystalline systems. Specific approaches for dealing with these shortcomings have been outlined within the context of the effective screening medium (ESM), 231,232 joint DFT (JDFT) [233][234][235] and self-consistent continuum solvation (SCCS) 230,236 methodologies. Alternative schemes for defining universal potential references for PEC-relevant reactions in DFT/AIMD have also been proposed.…”

Spicing up continuum solvation models with SaLSA: The spherically averaged liquid susceptibility ansatz

“…Unfortunately, the large number of parameters precludes the extrapolation of these models to systems outside their fit set, such as metallic or ionic surfaces in solution. Recent solvation models that employ an electron-density based parametrization [11,12] require only two or three parameters and extrapolate more reliably, but still encounter difficulties for charged and highly polar systems [13,14].The need for empirical parameters in continuum solvation arises primarily because of the drastic simplification of the nonlocal and nonlinear response of the real liquid with that of a continuum dielectric cavity. Recently, we correlated the dielectric cavity sizes for different solvents with the extent of nonlocality of the solvent response to enable a unified electron-density parametrization for multiple solvents [15], but the electron density threshold n c that determines the cavity size still required a fit to solvation energies of organic molecules.…”

“…In particular, the local models severely over-predict the solvation energies of small cations, and the nonlocal SaLSA model reduces the error by a factor of three for Li+ and Na+. However, SaLSA does not correct the systematic over-solvation of cations compared to anions, a known deficiency of electron-density based solvation models [13].…”

“…Unfortunately, the large number of parameters precludes the extrapolation of these models to systems outside their fit set, such as metallic or ionic surfaces in solution. Recent solvation models that employ an electron-density based parametrization [11,12] require only two or three parameters and extrapolate more reliably, but still encounter difficulties for charged and highly polar systems [13,14].…”