Towards a dissociative SPC-like water model – probing the impact of intramolecular Coulombic contributions

Abstract

The dissociative water potential introduced by Garofalini et al. proved to be a simple and effective description to account for proton transfer in aqueous media, enabling for instance the execution of simulation studies at different pH values. In this model the charge of each particle is represented by a point-charge surrounded by a Gaussian charge-cloud of opposite sign, thus four Coulombic terms (point-charge-point-charge, point-charge-charge-cloud, charge-cloud-point-charge and charge-cloud-charge-cloud) are required per atom pair. In this work it is demonstrated that the Gaussian charge distributions can be removed from the model after a minor modification of the overall atomic point-charges. Despite this substantial modification of the model, structural properties obtained via pair- and angle distributions remain largely unaffected and the change in dynamical properties (vibrational frequencies, proton transfer properties) was found to be minor. As an additional improvement an adjustment of the bending mode vibration was carried out by carefully evaluating the parametrization of the three-body interaction potential, thereby retaining the good agreement of the transfer properties of the aqueous excess proton reported in an earlier study. The proposed simple point-charge (SPC) type parametrization of the Coulombic interactions not only leads to a notable decrease in computational demand but generalizes the dissociative model by improving its transferability to established third-party simulation software and enabling the application of different theoretical approaches such as Ewald summation techniques not considered in the original parametrization. The outlined optimization strategy demonstrates that despite the complex and challenging formulation of the force field, various dynamical properties can be selectively adjusted without influencing other critical parameters of the simulated systems.

Chemosensing Test Paper Based on Aggregated Nanoparticles of a Barbituric Acid Derivative

“…Subsequently, all-atomic molecular dynamics simulations (MDS) were performed for the system in BIOVIA Materials Studio 2019 Forcite packages. The simple point charge (SPC) model [35,36], which can accurately describe the water solution environment [37], is adopted for all water molecules.…”

A DFTB/MM MD Approach for Solid-State Interfaces: Structural and Dynamical Properties of H2O and NH3on R-TiO2(001)

“…The advantage of executing a DFTB-based equilibration over standard force-field approaches is linked to the fact that the formation and cleavage of chemical bonds as required to describe proton-transfer reactions are inherently accounted for in DFTB approaches. Although a number of dissociative/reactive force fields for the treatment of aqueous solutions are available in the literature, − ,− ,− potential parameters to describe the surface–water interactions have to be provided, which are even more difficult in their construction/balancing compared to nondissociative MM formulations. Because dissociative force fields are typically benchmarked against QM-based simulation results, the outlined QM/MM strategy (at both DFTB and DFT levels) may provide key reference data to verify reactive force fields aimed at the description of proton-transfer reactions near solid-state interfaces.…”

Modelling bulk and surface characteristics of cubic CeO2, Gd2O3, and gadolinium-doped ceria using a partial charge framework

“…The main objective of the parametrization is to ensure compatibility between the novel derived solid-state potentials and the reactive water model. 28,29 The latter explicitly accounts for proton transfer reactions. Therefore, it is not possible to apply various atom types per element.…”

“…This procedure facilitates effective partial charges rather than relying on integer atomic charges derived from formal oxidation numbers. In addition, the parametrization strategy was based on parameters obtained from a dissociative water model, 28,29 which should enable integration of the novel potential model. A recent study 30 showed that extending a dissociative water model by including solid-state parameters allows MM MD to describe surface phenomena of heterogeneous systems, such as SiO 2 /H 2 O.…”