Dielectric relaxation computer simulation

In the second place, we shall study rotational dynamics. Rotational processes are of fundamental importance for dielectric relaxation. To shed light on some controversial issues in dielectric relaxation, Brot and co-workers did a computer simulation of a system of disks interacting via both Lennard-Jones potentials and electric dipole-dipole couplings. This is pre-... 

While the difference in the upwards and downwards solvent responses presented in Figure 3 is striking, this is not the first time that variations in solvation dynamics for the same solvent have been observed. Experimental studies have shown differences in solvation response for different probe molecules in the same solvent. This is a direct indication that probe molecules which have different excited state charge distributions and different mechanical interactions with the solvent produce differing relaxation dynamics. Computer simulations have also observed differing solvation dynamics for the forward and reverse transitions of the sudden appearance of charge, indicative of a solute-dependent solvent response. Moreover, theoretical work has shown that dielectric solvation dynamics is sensitive to the shape of a solute, and that solute size is intimately connected to viscoelastic relaxation. It is these effects which are manifest in the... 

M. Neumann, Dielectric relaxation in water. Computer simulations with the TIP4P potential, J. Chem. Phys., 85 (1986) 1567-1580. 

The molecular mechanisms for a number of these subglass transition relaxations have now been established, often by relating the temperature dependence of the frequency of the observed mechanical or dielectric relaxations to specific molecular motions, identified using either experiments (e.g., NMR and neutron scattering) or, more recently, computer simulations. By way of illustration, some examples of group motions that have been found to be active in a series of poly(alkyl methacrylate)s will be described in the following text. 

The dielectric relaxation (DR) spectrum of pure water has been investigated in considerable detail by different experimental techniques, such as dielectric loss and, more recently, terahertz spectroscopy. The DR of water has also been investigated by computer simulations. However, the computational efforts have been relatively less successful because of the difficulty of simulating polarizable water molecules. 

E. Dachwitz, F. Parak, and M. Stockhausen, On the dielectric relaxation of aqueous myoglobin solutions. Ber. Bunsenges. Phys. Chem., 93 (1989), 1454 S. Boresch, P. Hochtl, and O. Steinhauser, Studying the dielectric properties of a protein solution by computer simulation. J. Phys. Chem. B, 104 (2000), 8743-8752. 

Computer Simulation of Dielectric Relaxation at Metal-Insulator Interfaces... 

The volume is divided into three parts Part I. Metallization Techniques and Properties of Metal Deposits, Part II, Investigation of Interfacial Interactions," and Part III, "Plastic Surface Modification and Adhesion Aspects of Metallized Plastics. The topics covered include various metallization techniques for a variety of plastic substrates various properties of metal deposits metal diffusion during metallization of high-temperature polymers investigation of metal/polymer inlerfacial interactions using a variety of techniques, viz., ESCA, SIMS, HREELS, UV photoemission theoretical studies of metal/polymer interfaces computer simulation of dielectric relaxation at metal/insulalor interfaces surface modification of plastics by a host of techniques including wet chemical, plasma, ion bombardment and its influence on adhesion adhesion aspects of metallized plastics including the use of blister test to study dynamic fracture mechanism of thin metallized plastics. 

The full potential of dielectric relaxation spectroscopy in electrolyte studies is just emerging. This is due to important progress in instrumentation during the last 5-10 years, which now allows access of the relevant frequency region of 10 MHz-1 THz and beyond with relative ease. Also, quantitative computer simulation of ri (v) is coming into reach. This will provide a major step forward in the interpretation of dielectric spectra. 

The information presented in Sections 5.1.1.1-5.1.1.4 and Table 5.1, although construed to pertain to the effects of ions on the structure of the solvent, in the sense of whether it is enhanced or loosened by the presence of ions, actually reflects the effects on the dynamics of the solvent in the immediate neighborhood of the ions. The mean residence times of water molecules in the vicinity of ions are indirectly measures of the effect of the ions on the structure of the water as described in Section 5.2.1. There are aspects of solvent dynamics that are not covered by these effects, such as the orientational relaxation rate and hydrogen-bond lifetimes. Two experimental methods have mainly been employed for obtaining such information ultrafast mid-infrared and dielectric relaxation spectroscopy on the fs to ps time scales. Some slower processes were studied by NMR relaxation studies. Computer simulations added additional information, since it could be applied to individual ions rather than salts. As for the ion effects dealt with in the previous sections, the vast majority of the studies dealt with ions in aqueous solutions and only few ones considered ions in nonaqueous solvents... 

---