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Computer simulation generic models

The computer simulations are likely to be useful in two distinct situations— the first in which numerical data of a specified accuracy are required, possibly for some utilitarian purpose the second, perhaps more fundamental, in providing guidance to the theoretician s intuition, e.g., by comparing numerical results with those from approximate analytical approaches. As a consequence, the physical content of the model will depend upon the purpose of the calculation. Our attention here will be focused largely on the coarse-grained (lattice and off-lattice) models of polymers. Naturally, these models should reflect those generic properties of polymers that are the result of the chainlike structure of macromolecules. [Pg.7]

A variety of different models of the interface between water and a solid phase have been used in computer simulations. As far as the solid is concerned, a basic distinction can be made between smooth solid phases without atomic structure on the one hand and corrugated surfaces on the other. The latter surfaces have been modeled as rigid (frozen) or flexible atomic lattices representing the solid phase [47-51] or as a corrugated external potential that describes the effect of the solid phase by a more or less elaborate potential function F(x,y,z) [52-56]. The generic metallic features are modeled by treating the metal phase as a medium of infinite dielectric constant or by using the jellium model (e.g.. Ref. 57-59). In several cases, the results of semi-empirical and ab initio quantum chemical calculations have been parametrized [40, 48, 55]. [Pg.10]

The link energy is easier to measure and to interpret than to calculate from molecular models, because it is a function of the chemical details of the monomeric units and of the solvent and of the inherent bending stiffness of the polymeric species. Although that fairly generic features such as the influence of (screened) charges or of the bending stiffness are amenable to theoretical analysis, the link energy is inherently very sensitive to model approximations. Computer simulation may prove useful albeit that the issue of model sensitivity remains. [Pg.110]

It is probably fair to say that Monte Carlo simulations of model systems that are free of the sign problem (bosons, spin systems without frustration, and some special fermionic systems) have become so powerful that the properties of their quantum phase transitions can be determined quantitatively with high precision (see, e.g., the accuracy of some of the exponent values quoted in the preceding sections). For many frustrated spin systems, in contrast, the results are limited to a qualitative level, and for quantum phase transitions in generic fermionic systems (with sign problem), direct computational attacks are still of limited utility. [Pg.215]

For computationally simulating more dense two-phase flow systems, the Euler—Euler approach, based on the two-fluid model, is widely exploited. In this approach, the two phases are conceived as two interpenetrating con-tinua and the fact that the dispersed phase in real fife is made up by individual particles, drops, or particles is overlooked. The only term where particle size pops up is in the phase interaction force—see Eqs. (5) and (6)— for which empirical expressions derived from single-particle behavior are used which contain particle size in various ways. All above generic remarks about the combined use of the various correlations again apply however. [Pg.330]

The zeolite framework was described by a specific force field developed by van Santen et al. [11] while the hydrocarbon molecules and their interaction among themselves and with the zeolite lattice were described by the generic force field Drdding n [12]. All the internal coordinates of the alkane molecules were allowed to fully relax. The nonbonded interactions (electrostatic and van der Waals) were computed for aU atoms within a cutoff-radius of 12A. Periodic boundary conditions were imposed along the three axes of the zeolite model to simulate an infinite crystal. [Pg.43]

In this chapter we review our recent efforts towards understanding many of the salient features of detonation using NEMD simulations. We will focus on large-scale NEMD simulations using a model interatomic potential (denoted REBO) to study generic, but complex, detonation phenomena and the use of a new, computationally more intensive, potential (denoted ReaxFF) that accurately describes a real nitramine energetic material. [Pg.270]

Figure 2.1 illustrates this new approach. Simulation is placed in the core of the three main engineering activities Research Development, Design and Operation. The unifying matter is the scientific knowledge embedded in universal models, as well as the generic character of computational methods. These activities, apparently disconnected, can share a large number of first-principle models, as thermodynamics. [Pg.35]


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