Thermodynamic Description of Interfaces Applying the 2PT Method on ReaxFF Molecular Dynamics Simulations

Abstract

The interface between liquid water and the Pt(111) metal surface is characterized structurally and thermodynamically via reactive MD simulations within the ReaxFF framework. The formation of a distinct buckled adsorbate layer and subsequent wetting layers is tracked via the course of the water's density and the distribution of the H 2 O molecules with increasing distance to the metal surface. Hereby, also the two-phase thermodynamics (2PT) method has been utilized for studying the course of entropy as well as the translational, rotational, and vibrational entropic contributions throughout the Pt(111)|H 2 O interface. A significant reduction of the entropy compared to the bulk value is observed in the adsorbate layer (S = 31.05 ± 2.48 J/mol K) along with a density of 3.26 ± 0.06 g/ cm 3 . The O−O interlayer distribution allows for direct tracing of the water ordering and a quantified comparison to the ideal hexagonal adlayer. While the adsorbate layer at the Pt surface shows the occurrence of hexagonal motifs, this near-order is already weakened in the wetting layers. Bulk behavior is reached at 15 Å distance from the Pt(111) metal. Introducing an electric field of 0.1 V/Å prolongs the ordering effect of the metal surface into the liquid water. ■ METHODS2PT Method: Formalism. The 2PT algorithm begins by calculating the total VACF C(t) as the mass weighted sum of the respective atom VACFs c j k

Fundamentals of energy storage from first principles simulations: Challenges and opportunities

“…(1941). Jung et al (2021) applied the two-phase thermodynamics (2PT) approach (Lin et al, 2010;Pascal et al, 2011) and computed entropy of aqueous phase as a function of distance from the Pt(111) interface. Here we applied the 2PT approach to evaluate different entropy contributions for HCOOH molecules submerged in aqueous phase, in the bulk and at the Pb(100) and Ag (100) surfaces.…”

Potential‐Dependent Pt(111)/Water Interface: Tackling the Challenge of a Consistent Treatment of Electrochemical Interfaces**

“…We have successfully transferred the Two Phase Thermodynamics method (2PT) to the ReaxFF framework and the Pt(111)/ H 2 O interface for a structural and thermodynamical characterization thereof, see Ref. 43. This method constitutes the calculation of thermodynamical quantities by merely postprocessing a molecular dynamics trajectory, dividing the density of states function of the liquid into a superposition of solid and diffusive contributions and thereon applying the respective thermodynamic theories.…”

“…In the present work we present a self-consistent approach to handle the electrode potential in electrochemical interfaces, [43] (b) Oxygen distribution in z direction with increasing distance from the Pt surface for 0.37 V and 0.95 V electrode potential. Characteristic PtÀ H 2 O distances are labelled for comparison.…”

“…For a detailed description of the method as well as the coupling between the 2PT method (developed by Lin et al [45,46] ) and ReaxFF, we refer the reader to our recent publication. [43] Structure visualizations were performed using VMD software. [47]…”

How to Gain Atomistic Insights on Reactions at the Water/Solid Interface?

“…For instance, ReaxFF has recently been used to investigate the dissociative adsorption and decomposition of acetic acid at the ZnO/water interface in function of the temperature. 81 Moreover, such simulations also give access to the entropy at the solid/water interface, 82 which will ultimately enable a fundamental understanding of the thermodynamic differences in reactivity between gas-phase, solution-phase, and the water/solid interface.…”