Atomistic computational methods

Quantum mechanical calculations on small clusters can also provide interatomic potentials which can then be used to predict the stabilities of complexes in bulk fluids using classical molecular dynamics or Monte Carlo simulations. Such calculations can be very successful in predicting metal speciation and equations of state of complex electrolytes. In this chapter I will first outline the theoretical approximations used in the quantum chemistry of metal complexes. In parts two and three, I will illustrate the 

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Since the development and application of atomistic computational methods in recent years, our understanding of gas microfluidics and nanofluidics has been greatly improved. If the flow and thermal behavior can be correctly analyzed and accurately predicted, optimal design of microsystems is possible. Related work can be found in analyses of the performance of microscale air slide bearings in hard disk drives [16], the propulsion efficiency of micronozzles in... 

Very recently, people who engage in computer simulation of crystals that contain dislocations have begun attempts to bridge the continuum/atomistic divide, now that extremely powerful computers have become available. It is now possible to model a variety of aspects of dislocation mechanics in terms of the atomic structure of the lattice around dislocations, instead of simply treating them as lines with macroscopic properties (Schiotz et al. 1998, Gumbsch 1998). What this amounts to is linking computational methods across different length scales (Bulatov et al. 1996). We will return to this briefly in Chapter 12. 

On the other hand, based on the rapid progress which was recorded in the last decade in the atomistic simulation of diffusion processes in polymers one may be confident that these computational methods will be one day able to cope with the prob-... 

CONTENTS Introduction, Thom H. Dunning, Jr. Electronic Structure Theory and Atomistic Computer Simulations of Materials, Richard P. Messmer, General Electric Corporate Research and Development and the University of Pennsylvania. Calculation of the Electronic Structure of Transition Metals in Ionic Crystals, Nicholas W. Winter, Livermore National Laboratory, David K. Temple, University of California, Victor Luana, Universidad de Oviedo and Russell M. Pitzer, The Ohio State University. Ab Initio Studies of Molecular Models of Zeolitic Catalysts, Joachim Sauer, Central Institute of Physical Chemistry, Germany. Ab Inito Methods in Geochemistry and Mineralogy, Anthony C. Hess, Battelle, Pacific Northwest Laboratories and Paul F. McMillan, Arizona State University. 

Computational methods have had a major impact on almost all areas of science in recent years. The range of applications is now very broad, encompassing molecular biology, materials and surface science, mineralogy, and small molecule chemistry. This article focuses on the application of atomistic computer modeling techniques to materials science. We present a brief survey of the aims and scope of the field and short introduction to the main methodologies. We illustrate the current state of the art of computer modeling studies of materials by recent applications to bulk and surface properties of topical systems. 

Polymer science has undergone a transition recently. Many of the traditional computational tools used for atomistic molecular modeling are now being used in polymer science. In Chapter 3, Professor Vassilios Galiatsatos provides an account of how these modern computational methods are being implemented and refined by polymer scientists to complement existing theories developed by Flory, DeGennes, and others. The focus here is on homopolymers. 

Jayaraman and Maginn calculated two crystal polymorphs of [C4mim][Cl] using a thermodynamic integration-based atomistic simulation method [78]. The computed... 

Empirical correlations [21] and computationally-intensive large-scale atomistic simulations [27-42] have been mentioned above as opposite extremes in the spectrum of methods used to treat diffusion phenomena. In addition, two general types of phenomenological theories (which are much more sophisticated than empirical correlations, but much more coarse-grained than atomistic simulation methods) have been developed to treat diffusion ... 

In this chapter we show how atomistic computer simulation methods can yield unique insights into the structural properties of amorphous solids. The range and scope of the materials that can currently be studied by modelling techniques is illustrated by recent results, predominantly on glassy materials (defined below), although a brief discussion of other classes of amorphous materials is given towards the end of the chapter. 

In addition to the classical force fields above, many other force fields have been developed for small drug molecules or macromolecules. The MM2, MM3, and MM4 force fields were developed by Norman L. Allinger for a broad range of chemicals, and CFF is a family of force fields adapted to a broad variety of organic compounds, polymers, metals, and so on. The MMFF force field was developed at Merck for a broad range of chemicals. ReaxFF is a reactive force field, developed by William Goddard and coworkers, is fast, transferable, and the computational method of choice for atomistic-scale dynamics simulations of chemical reactions. 

Welder T, Walther JH, Koumoutsakos P (2005) Hybrid atomistic-continuum method for the simulation of dense fluid flows. J Comput Phys 205 373-390... 

Generally, the two simplest and most common models for the mechanical properties of fiber reinforced composites are the rule of mixtures and the Halpin-Tsai equations [71]. The computational methods for the investigation of CNTs and CNT-filled composites can be categorized into two classes continuum methods and atomistic methods [31]. 

Like other multiscale methods, atomistic-continuum methods require an accurate treatment of the coupling between different domains. In addition to these difficulties, they pose serious challenges for performing extensive simulations. The physical processes described by continuum equations and particle-based models impose inherently distinct demands on the computer architerture. While continuum mechanics and hydrodynamics, typically dealing with regular meshes, are characterized by moderate computations with stractured communications, atomistic simulations are characterized by intense computations and intense interprocessor communications. As a result, large-scale simulations of this sort require a balanced computer architecture in terms of memory bandwidth and interconnea bandwidth. 

Abstract A variety of computational procedures used to predict properties of energetic materials is presented. These procedures, based on standard atomistic simulation methods, demonstrate the ability to predict key properties of these materials related to performance or hazard. Several applications of the various methods for nitrogen-rich materials are provided to illustrate capabilihes. Also, an overview of theoretical efforts in computational design of novel all-nitrogen materials is given. 

The theoretical methods that will be discussed in this chapter represent only a subset of the various atomistic simulation methods used in computational materials research, and we refer the interested reader to the various comprehensive reviews on each method [22-30]. For the purposes of this chapter, however, we will highhght important points associated with various theories in appUcation to the high nitrogen materials. 

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