Near metal surfaces, computer

E. Spohr. Computer simulaton of the structure and dynamics of water near metal surfaces. In G. Jerkiewicz, M. P. Soriaga, K. Uosaki, A. Wieckowski, eds. Solid-Liquid Electrochemical Interfaces, Vol. 656 of ACS Symposium Series. Washington ACS, 1997, Chap. 3, pp. 31-44. 

Computer Simulation of the Structure and Dynamics of Water Near Metal Surfaces... 

Adsorption energy, effect on density, computer simulation of structure and dynamics of water near metal surfaces, 34-36... 

Chapter 1 introduces the basic foundations of molecular plasmonics. It is a self-contained chapter, starting with Maxwell s equations and concluding with the derivation of the radiative and non-radiative decay rates of emitting molecules near metal surfaces and nanoparticles. After this introductory chapter, the handbook is subdivided in two parts the first one describes the computational and theoretical methods of interest in molecular plasmonics, while the second is entirely dedicated to the most relevant applications and experimental techniques. Both parts contain precious contributions from international experts to ensure a plurality of points of view. 

The modification of theoretical gas-phase reaction techniques to study gas-surface reactions continues to hold promise. In particular, the LEPS formalism appears to capture a sufficient amount of realistic bonding characteristics that it will continue to be used to model gas-surface reactions. One computational drawback of the LEPS-style potentials is the need to diagonalize a matrix at each timestep in the numerical integration of the classical equations of motion. The size of the matrix increases dramatically as the number of atoms increases. Many reactions of more direct practical interest, such as the decomposition of hydrocarbons on metal surfaces, are still too complicated to be realistically modeled at the present time. This situation will certainly change in the near future as advances in both dynamics techniques and potential energy surfaces continue. 

It is increasingly realized that many-body induction interactions should be included in computer models, especially in inhomogeneous environments. Kohlmeyer et al. [44] therefore investigated the role of molecular polarizability on the density profiles of a slab of water in contact with several different metal surfaces. They employed the polarizable TIP4P model by Rick and Berne [46]. It was found that the density profiles are almost identical near a metallic surface the liquid/gas interface appears to become slightly wider. Earlier studies of polarizable water at a hydro-phobic wall by Wallqvist [141] and near the liquid/gas interface by Motakabbir and Berkowitz [142] also concluded that polarization effects are of secondary importance. 

On the whole, current studies of metal-water interfaces are restricted to fairly flat surfaces, free of irregularities. Study of an SPM tip near a metal surface in the presence of water is a notable exception." The treatment of irregular surfaces presents a significant challenge in this area of computational chemistry, partly because of the lack of information concerning the nature of the interaction of water molecules with defects in metal surfaces. Similarly, an understanding of the dynamics of metal atoms in these systems is required. Here again, appropriate quantum mechanical calculations will likely be important for further development. 

We start with the simplest model of the interface, which consists of a smooth charged hard wall near a ionic solution that is represented by a collection of charged hard spheres, all embedded in a continuum of dielectric constant c. This system is fairly well understood when the density and coupling parameters are low. Then we replace the continuum solvent by a molecular model of the solvent. The simplest of these is the hard sphere with a point dipole[32], which can be treated analytically in some simple cases. More elaborate models of the solvent introduce complications in the numerical discussions. A recently proposed model of ionic solutions uses a solvent model with tetrahedrally coordinated sticky sites. This model is still analytically solvable. More realistic models of the solvent, typically water, can be studied by computer simulations, which however is very difficult for charged interfaces. The full quantum mechanical treatment of the metal surface does not seem feasible at present. The jellium model is a simple alternative for the discussion of the thermodynamic and also kinetic properties of the smooth interface [33, 34, 35, 36, 37, 38, 39, 40]. 

The rough electrode near a non primitive electrolyte. This is a case relevant to computer simulations of realistic solvent models near a model of a metallic surface such as the silver( 111) surface, for which experiments have recently been reported [61]. Most models of water employed in the computer simulations consist of neutral molecules with embedded point charges. 

Chance, Frock and Silbey [28] computed explicit expressions for the normalized decay rates near a metal surface, expanding the dipolar field in plane-waves and considering for each of them the reflection coefficients from the metal substrate ... 

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