Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X19: Modeling the Electrochemical Interface and Aqueous SolutionsFocus Live
|
Hide Abstracts |
Sponsoring Units: DCOMP DCP Chair: Marivi Fernandez-Serra; Luana Pedroza, Univ Federal do ABC |
Friday, March 19, 2021 8:00AM - 8:36AM Live |
X19.00001: Addressing electrified metal-electrolyte interfaces with Non-Equilibrium Green's Functions Invited Speaker: Pablo Ordejon We demonstrate how Non-Equillibrium Green's Functions techniques can be used to address, from first principles, the atomistic description of metal-electrolyte interfaces in the presence of an external bias applied to the electrodes. The NEGF method allows to deal with open, non-periodic systems driven out of equillibrium by the external applied bias. We use the TranSIESTA method and code [1,2], developed within the SIESTA project [3]) to study problems involving steady-state non-equilibrium situations in nanoscale costrictions, where an external electric bias is applied between the two sides of the constriction, establishing a steady electric current. We show how this computational machinery can be also used to study electrified solid/liquid interfaces [4], where an external bias is applied to the solid electrode. Here, one is not concerned with the quantum electronic transport, but with the effect of the external bias on the structural changes, dynamics and chemical reactions induced at the metal/liquid interface. I will show molecular dynamic simulations of aqueous electrolytes as a proof of concept for future realistic, atomistic first-principles simulations of electrochemical processes. |
Friday, March 19, 2021 8:36AM - 8:48AM Live |
X19.00002: Demystifying the Stern layer at metal-electrolyte interface: Local dielectric constant, ion adsorption and partial charge transfer Xuepeng Wang, Jianzhong Wu Electric double layer (EDL) models are commonly used in electrochemical sciences and diverse applications. Whereas phenomenological models have been long established to describe ionic distributions, a faithful description of the electrode-electrolyte interface remains a daunting challenge. In this work, we study the charging behavior of Ag (111) electrode in NaF aqueous solutions by a combination of experimental results with theoretical calculations based on the Gouy-Chapman–Stern (GCS) model, the classical density functional theory (cDFT), and the joint density functional theory (JDFT). When the electrode is negatively charged, the ionic distribution can be described by the GCS/cDFT model with the dielectric constant of the Stern layer depending on the local electric field. F- adsorption in the Stern layer takes place when the electrode is positively charged and can be attributed to both physical and chemical interactions. The chemisorption exhibits partial charge transfer from F- to the Ag that depends on the applied voltage. Qualitatively, F- binding and partial charge transfer are supported by the JDFT calculations. Our findings shed insights on the characteristics of the Stern layer and the charge behavior of adsorbed species not specified by conventional EDL models. |
Friday, March 19, 2021 8:48AM - 9:00AM Live |
X19.00003: Coulomb Screening Effects on Solvated Ions Alec Wills, Marivi Fernandez-Serra Potentials of mean force of ions in solution are used to explore the energetics of solvation. From them, the stability of solvation states yields insight into how ions might behave in physical solution. However, results arising from simulations with different parameters frequently contradict. Decomposing the free energy of solvation into enthalpic and entropic contributions can help our understanding of what drives the energetic results obtained from any specific set of simulation parameters. Moreover, intuition of the effects ions have on the solution requires an understanding of the strength that ions are screened from the bulk. In an effort to model the effects of charge screening on ion pair stability, we present a linear response model that modifies the Coulomb potential and gives an alternate understanding of solvation transition barriers. Moreover, it predicts stable Coulombic pairings between like-charged ions, which we show exist in simulation. This allows us to better understand enthalpic contributions to the free energy of solvation, and helps to isolate entropic effects for further study. |
Friday, March 19, 2021 9:00AM - 9:36AM Live |
X19.00004: First-principles electrochemistry with grand-canonical DFT and continuum-solvation methods Invited Speaker: Ravishankar Sundararaman First-principles calculations combining density-functional theory (DFT) and continuum solvation models have been highly successful in enabling the theoretical design of liquid-phase catalyst materials. The application of such methods to heterogeneous catalysis in electrochemical solid-liquid interfaces has however been far more challenging for two reasons. First, conventional continuum solvation methods designed for finite molecular systems are not readily applicable to solid-liquid interfaces with metal or oxide surfaces. Second, processes at these interfaces continuously exchange electrons with the electrode, which makes the charge states of the surface difficult to determine. |
Friday, March 19, 2021 9:36AM - 9:48AM Live |
X19.00005: Polarizable Classical Force Field to Describe the Water/Metal Interfaces in QM/MM Simulations of Electrochemical Interfaces Márcio Gomes-Filho, Aline Olimpio Pereira, Luana Pedroza, Gustavo T. Feliciano, Maurício D. Coutinho-Neto Electrochemical interfaces are of extreme importance for several technological applications (e.g, fuel cells and biological sensors). However, the microscopic understanding of the kinetic behavior and reactions that occur in water/metal interfaces is still a challenge. Thus, atomistic simulations have proven to be a versatile tool to provide a detailed comprehension of such interfaces at the atomic level. In particular, the mutiscale QM/MM simulations, which take in account both the quantum information and the size of such systems, seem to be an efficient approach to describe the electrode interface. One of the key elements in QM/MM approaches is the classical force field. Particularly for metals, the accuracy of the simulation strongly relies in the ability of the force field to reproduce surface polarization (SP) effects. Based on this, we develop suitable polarizable force fields to describe the water/metal interface. Charged virtual sites (rods) are added to the molecular topology of a simple LJ model in order to create dipoles that reproduce the SP and adsorption properties of the metallic surfaces. We select the water/metal interfaces composed by Pd(111) as model systems to evaluate the performance of the proposed models. |
Friday, March 19, 2021 9:48AM - 10:00AM Live |
X19.00006: Photogenerated electron-hole charge separation in oxide perovskite [001] surfaces Vidushi Sharma, Benjamin Bein, Amanda Lai, Betul Pamuk, Marivi Fernandez-Serra, Matthew Dawber Perovskite oxides such as SrTiO3 have garnered much interest owing to their high photocatalytic efficiency and favorable interfacial interactions with water, two important features that drive solar water splitting. Understanding their behavior in aqueous environments is critical to improving their performance in energy applications. In this work, we focus on the overall water splitting reaction at SrTiO3 [001] surfaces initiated by photogenerated electron-hole pairs. Using a combination of first-principles simulations and experiments, we elucidate the relation between spatial electron-hole charge separation and photocatalytic activity on the surface. Since [001] SrTiO3 surfaces present two different terminations, namely TiO2 and SrO, we identify which one is better suited for a photo-oxidation or reduction. This provides crucial insight into the nature of water-splitting reactions occurring at a water-oxide interface. We consider explicitly the effect of an excess electron (resp. hole) by introducing electron (resp. hole)-rich dopants at Ti-sites. We find that the preferential migration of a charge carrier is strongly determined by the specific surface site as well as the surface termination of the site. |
Friday, March 19, 2021 10:00AM - 10:12AM Live |
X19.00007: First principles molecular dynamics of electrified silicon/water interfaces Zifan Ye, Aleksander Prominski, Bozhi Tian, Giulia Galli Si-based materials have been used in a myriad of devices, including as cathodes in photoelectrochemical cells and p-i-n junctions in optoelectronic bio-modulators. In both cases, the surfaces are in contact with water, and the interface is under the effect of an electric field. We built an atomistic model of the hydrogenated Si(100) surface in contact with water and we carried out first principles simulations in the presence of an electric field aimed at understanding faradic and capacitive processes at the interface. Simulations were carried out with the Qbox code (http://qboxcode.org). Our calculations of flat-band potentials reveal how doping or applied electric fields affect capacitive processes. Specifically, we find that highly doped p-i-n Si junctions are desired to obtain larger capacitive currents. In addition, our calculations of 2D scanning tunneling current images at the interface show that small faradic currents may originate from the oxidation of Si-H bonds by water molecules, and we suggest these currents should be detectable by patch clamp measurements. |
Friday, March 19, 2021 10:12AM - 10:24AM Live |
X19.00008: Analytical form for polarization induced self-energy for ions in solution near rough substrates. Francisco Solis In addition to the direct Coulomb interaction, ions in solution experience polarization mediated interactions. These appear as confining solid walls for an electrolyte typically have a dielectric constant different from that of the solution bulk and therefore exhibit polarization. Electrostatic interaction with the polarization charge induces interactions between pairs of ions as well as an excess self-energy for individual ions. This self-energy has been shown to produce important surface effects. Mean field theories for the solution, such as Poisson-Boltzmann, require modifications to include the self-energy effect. Explicit expressions for the self-energy are therefore necessary. For flat interfaces, these can be calculated using image charges while for more complex geometries only computational methods are available. This presentation considers the effect of roughness in near flat surfaces. The polarization charge and the self-energy of an ion near the surface are calculated using perturbation theory to first order on the amplitude of the roughness. To this order, explicit analytical expressions for the self-energy are obtained. Some consequences of the structure of these solutions are described. |
Friday, March 19, 2021 10:24AM - 10:36AM Live |
X19.00009: Electrostatic wetting transition: charge inversion and like charge attraction Nikhil Agrawal, Rui Wang The study of the Electrical Double Layer lies at the heart of soft matter physics. In the so-called weak coupling limit, mean-field Poisson Boltzmann has enjoyed significant successes, but the absence of ionic correlations does not allow it to even qualitatively explain many fundamental moderate and strong coupling phenomena such as charge inversion and like-charge attraction. Here we develop a Gaussian fluctuation theory that self-consistently includes ion-ion correlations and excluded volume effect. Our theory predicts an ionic correlation induced liquid-like boundary layer on the surface. In the intermediate salt concentration regime, this wetting transition results in charge inversion. At higher concentrations, the charge inversion disappears, and the effective charge regains its original sign. Our theoretical results are in good agreement with both experiments and simulations. |
Friday, March 19, 2021 10:36AM - 10:48AM Not Participating |
X19.00010: Metastability Triggered Reactivity in Clusters at Realistic Conditions: A Case Study of N-doped (TiO2)n for water splitting Shikha Saini, Saswata Bhattacharya
|
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700