First-principles molecular dynamics simulations at solid-liquid interfaces with a continuum solvent

Abstract

Continuum solvent models have become a standard technique in the context of electronic structure calculations, yet no implementations have been reported capable to perform molecular dynamics at solid-liquid interfaces. We propose here such a continuum approach in a density functional theory framework using plane-wave basis sets and periodic boundary conditions. Our work stems from a recent model designed for Car-Parrinello simulations of quantum solutes in a dielectric medium [D. A. Scherlis et al., J. Chem. Phys. 124, 074103 (2006)], for which the permittivity of the solvent is defined as a function of the electronic density of the solute. This strategy turns out to be inadequate for systems extended in two dimensions: the dependence of the dielectric function on the electronic density introduces a new term in the Kohn-Sham potential, which becomes unphysically large at the interfacial region, seriously affecting the convergence of the self-consistent calculations. If the dielectric medium is properly redefined as a function of the atomic coordinates, a good convergence is obtained and the constant of motion is conserved during the molecular dynamics simulations. The Poisson problem is solved using a multigrid method, and in this way Car-Parrinello molecular dynamics simulations of solid-liquid interfaces can be performed at a very moderate computational cost. This scheme is employed to investigate the acid-base equilibrium at the TiO(2)-water interface. The aqueous behavior of titania surfaces has stimulated a large amount of experimental research, but many open questions remain concerning the molecular mechanisms determining the chemistry of the interface. Here we make an attempt to answer some of them, putting to the test our continuum model.

Ab Initio Electrochemical Properties of Electrode Surfaces

“…The parameters of the electrochemical model are selected to be e S ¼ 78, k B T ¼ 0.0025 Ry, r 0 ¼ 0.0005 bohr À3 , r 1 ¼ 0.0001 bohr À3 , and b ¼ 1. 25. We observe that while the error in E is on the order of 0.5 eV using homogeneous Dirichlet boundary conditions, the potential rapidly converges within a few millielectronvolts using electrochemical boundary conditions.…”

“…Another possible alternative is to redefine the dielectric function as a function of atomic coordinates to eliminate the dependence of the dielectric constant with respect to the self-consistent charge density [24,25].…”

CO2 Capture and Conversion on Rutile TiO2(110) in the Water Environment: Insight by First-Principles Calculations

“…The solvation effect are efficiently screened in the presence of the dielectric medium. 46 As mentioned in the introduction, photo-catalytic reduction of CO 2 on the TiO 2 surface has attracted great attentions. Whereas the understanding on the reaction mechanism in aqueous solution at the molecular level is rather rare, we focus on the adsorption configuration and reactivity properties of CO 2 and H 2 O co-adsorption on rutile (110) surface including the solvation effect.…”

Multigrid-Based Methodology for Implicit Solvation Models in Periodic DFT

“…26,27 Although the arithmetic cost of multigrid is of O(N), while FFT-based methods require O(N log N) operations (N is the system size), the use of such methods in the context of implicit solvation models is less extended, and usually restricted to small systems. 25,32 Indeed, the multigrid algorithm depends on a large number of parameters (e.g., the order of accuracy of the transfer operators between grids, the discretization order of the fine-grid differential equation, the total number of grids, or the number of smoothing cycles). Therefore, an inefficient implementation of the algorithm with respect to all these parameters can result in a high computational cost.…”