A5068546520- nanoparticles nucleation surface interactions
- Advanced Chemical Physics Studies
- Surface and Thin Film Phenomena
- Gold and Silver Nanoparticles Synthesis and Applications
- Spectroscopy and Quantum Chemical Studies
- Theoretical and Computational Physics
- Quantum Dots Synthesis And Properties
- Material Dynamics and Properties
- Molecular Junctions and Nanostructures
- Surface Modification and Superhydrophobicity
- Surfactants and Colloidal Systems
- Nanomaterials for catalytic reactions
- Nanomaterials and Printing Technologies
- Surface Chemistry and Catalysis
- Catalytic Processes in Materials Science
- Pickering emulsions and particle stabilization
- Electrostatics and Colloid Interactions
- Machine Learning in Materials Science
- Fluid Dynamics and Heat Transfer
- Advanced Materials Characterization Techniques
- Copper-based nanomaterials and applications
- Advanced Physical and Chemical Molecular Interactions
- Semiconductor materials and devices
- Advanced Thermodynamics and Statistical Mechanics
- Phase Equilibria and Thermodynamics
Pennsylvania State University
2016-2025
Park University
2016-2023
Institute of Chemical Engineering
1993-2015
University of Michigan
1986-1991
Monte Carlo methods are utilized as computational tools in many areas of chemical physics. In this paper, we present the theoretical basis for a dynamical method terms theory Poisson processes. We show that if: (1) ‘‘dynamical hierarchy’’ transition probabilities is created which also satisfy detailed-balance criterion; (2) time increments upon successful events calculated appropriately; and (3) effective independence various comprising system can be achieved, then may to simulate process...
We describe a theoretical study of the role adsorbate interactions in island nucleation and growth, using Ag/Pt(111) heteroepitaxy as an example. From density-functional theory, we obtain substrate-mediated Ag adatom pair interaction find that, past short range, repulsive ring is formed about adatoms. The magnitude repulsion comparable to diffusion barrier. In kinetic Monte Carlo simulations, that lead densities over order larger than those predicted by theory thus identify severe limitation...
We use density functional theory to resolve the role of polyvinylpyrrolidone (PVP) in shape-selective synthesis Ag nanostructures. At segment level, PVP binds more strongly Ag(100) than Ag(111) because a surface-sensitive balance between direct binding and van der Waals attraction. chain correlated leads strong preference for bind Ag(100). Our study underscores differences small-molecule polymeric structure-directing agents.
Oriented attachment (OA) of nanocrystals is now widely recognized as a key process in the solution-phase growth hierarchical nanostructures. However, microscopic origins OA remain unclear. We perform molecular dynamics simulations using recently developed ReaxFF reactive force field to study aggregation various titanium dioxide (anatase) vacuum and humid environments. In vacuum, merge along their direction approach, resulting polycrystalline material. By contrast, presence water vapor...
We studied the adsorption and dissociation of water at 300 K on following TiO2 surfaces: anatase (101), (100), (112), (001), rutile (110) various coverages, using a recently developed ReaxFF reactive force field. The molecular dissociative configurations predicted by for coverages agree with previous theoretical studies experiment. predicts complex distribution these surfaces depending an intricate balance between spacing sites (under-coordinated Ti O surface atoms), water–surface...
Chloride (Cl-) is often used together with polyvinylpyrrolidone (PVP) in the polyol synthesis of Ag nanocubes. In literature, shape control attributed predominantly to preferential binding PVP Ag(100) facets compared Ag(111) facets, whereas role Cl- has not been well studied. Several hypotheses have proposed regarding Cl-; however, there still no consensus exact influence shape-controlled To examine Cl-, we undertook a joint theoretical-experimental study. Experimentally, examined...
The importance of structure-directing agents (SDAs) in the shape-selective synthesis colloidal nanostructures has been well documented. However, mechanisms by which SDAs actuate shape control are poorly understood. In polyvinylpyrrolidone (PVP)-mediated growth {100}-faceted Ag nanocrystals, this capability attributed to preferential binding PVP Ag(100). We use molecular dynamics simulations probe atoms add Ag(100) and Ag(111) ethylene glycol solution with PVP. find that induces kinetic...
Superhydrophobic surfaces often incorporate roughness on both micron and nanometer length scales, although a satisfactory understanding of the role this hierarchical in causing superhydrophobicity remains elusive. We present two-dimensional thermodynamic model to describe wetting hierarchically grooved by droplets for which influence gravity is negligible. By creating phase diagrams with single-scale roughness, we find that leads greatly expanded superhydrophobic domains space over those...
Shape-control is used to tune the properties of metal nanostructures in applications ranging from catalysts touch screens, but origins anisotropic growth nanocrystals solution are unknown. We show single-crystal electrochemistry can test hypotheses for why form and predict conditions by quantifying degree which different species cause facet-selective deposition. Electrochemical measurements disruption alkylamine monolayers chloride ions causes Cu An intermediate range concentrations...
We present a new method for accelerating molecular-dynamics simulations of infrequent events. The targets simulation systems that spend most the time in local energy minima, with slow transitions between, as is case low-temperature surface diffusion. potential-energy modified by adding boost potential regions close to such all transition rates are increased while relative preserved. an empirical function determined deviation bond lengths specified set atoms from equilibrium. requires no...
We find a noise-induced transition to bistability in Monte Carlo simulation of model heterogeneous catalytic chemical reaction which is deterministically monostable. Analysis the probability density function and correlation integral time series this indicates existence central role noise transition. that behavior system consequence interaction with spatial degrees freedom on surface.
We use dispersion-corrected density functional theory (DFT) to resolve the role of polyvinylpyrrolidone (PVP) in shape-selective synthesis Ag nanostructures by probing interaction its 2-pyrrolidone (2P) ring with Ag(100) and Ag(111). employ two different semiempirical methods for including van der Waals (vdW) interactions DFT calculations: DFT+vdWsurf DFT-D2. find that DFT-D2, original parametrization, overestimates metal dispersion causes an unphysical herringbone-like reconstruction...
We use classical molecular-dynamics simulations to study the aggregation of various titanium dioxide (anatase) nanocrystals in vacuum. In all cases, we observe a strong tendency for aggregate with certain preferred orientations "hinge" mechanism. Although some possess significant dipole moments, dipole−dipole interactions do not direct aggregation, implying that higher-order multipole moments are driving force preferential alignment. These high-order originate from under-coordinated O and Ti...
In this work, we investigate the dynamic advancing and receding contact angles, mechanisms of motion water droplets moving across nanopillared superhydrophobic surfaces using molecular-dynamics simulation. We obtain equilibrium Cassie states on with different pillar heights, groove widths, intrinsic angles. quantitatively evaluate angles along direction an applied body force, find that they depend roughness parameters force in a predictable way. The maximum angle is 180°, minimum close to...
This study demonstrates the crucial role of reduction kinetics in phase-controlled synthesis noble-metal nanocrystals using Ru as a case study. We found that played more important than templating effect from preformed seed dictating crystal structure deposited overlayers despite their intertwined effects on successful epitaxial growth. By employing two different polyols, series with tunable sizes 3-7 nm and distinct patterns phase were synthesized by incorporating types seeds. Notably, use...
We use molecular-dynamics simulations and importance sampling to obtain transition-state-theory rate constants for thermal desorption of an n-alkane series from Au(111). find that the binding a large molecule solid surface involves different types local minima. The preexponential factors increase with increasing chain length can be substantially larger than typical estimates small molecules. Our results match recent experimental studies indicate proper treatment conformational isomerism...
We show that attractive interactions between molecules adsorbed in molecular sieves play a vital role the mechanisms and rates of intracrystalline diffusion. Over wide temperature range, single-file diffusion ${\mathrm{CF}}_{4}$, ${\mathrm{SF}}_{6}$, ${\mathrm{CCl}}_{4}$ ${\mathrm{AlPO}}_{4}$- $5$ is dominated by clusters. ${\mathrm{SF}}_{6}$ clusters diffuse concerted involving all cluster's simultaneously. The activation energies, ${E}_{a}$, for these are strongly size dependent lower than...
The islands of adsorbed molecules in an $A+B\ensuremath{\rightarrow}\mathrm{AB}$ reaction model on a two-dimensional catalyst surface (with no diffusion) are found to be fractal with dimension $D=1.90\ifmmode\pm\else\textpm\fi{}0.03$.
We present a local superbasin kinetic Monte Carlo (LSKMC) method that efficiently treats multiple-time-scale problems in (KMC). The is designed to solve the small-barrier problem created by groups of recurrent free-energy minima connected low barriers and separated from full phase space system high barriers. propose an algorithm detect, on fly, consolidate them into “superbasins,” which we treat with rate equations and/or absorbing Markov chains. discuss various issues involved implementing...
This article shows how the chain length of alkylamine capping agents and corresponding stability their self-assembled monolayers on a Cu surface determines growth rate, yield, dimensions nanowires produced in solution-phase synthesis. Of 10 linear alkylamines that were tested, only those with 12 or more carbon atoms induced nanowires. The length, rate larger for shorter alkylamines. As nanowire rates up to 1050 times smaller than calculated diffusion-limited rates—and had no significant...
Kristen Fichthorn opened the discussion of introductory lecture by James De Yoreo: I noted that in your potential mean force (PMF) plots for various particle orientations, fluctuations occur such different orientations could be preferred at a fixed distance. Could this affect ag
Solution-phase synthesis of metal nanocrystals with multiple additives is a common strategy for control over nanocrystal shape, and thus their properties. However, few rules are available to predict the effect capping agents on shapes, making it hard rationally design synthetic conditions. This work uses combination seed-mediated growth, single-crystal electrochemistry, DFT calculations determine roles PVP Cl- in anisotropic growth penta-twinned silver nanocrystals. Single-crystal seeds grow...
Twin structures possess distinct physical and chemical properties by virtue of their specific twin configuration. However, twinning detwinning processes are not fully understood on the atomic scale. Integrating in situ high resolution transmission electron microscopy molecular dynamic simulations, we find tensile strain asymmetrical 5-fold twins Au nanoparticles leads to boundary migration through dislocation sliding (slipping an layer) along boundaries reactions at axis under beam....