Paraffin crystals simulation

The simulations of paraffin crystals was also carried out with a full-atom model in which hydrogens are explicitly included, making the size of a crystal about 30,000 atoms [18]. As expected from the proper rotational potentials used in the united atom model, the gauche concentration and lattice parameter distribution are not significantly different when the H-atoms are included explicitly. The observed crystal structure was, surprisingly, as mentioned above, also not close to experimental equilibrium paraffin structure, an indication that further work is needed to find the subtle adjustment needed in the intermolecular force field that governs the stable crystal structure, or develop simulations of... 

An understanding of both the microscopic structure and dynamics of matter is essentia] for a full description of its macroscopic properties. In this regard, recent studies of the internal dynamics of paraffin- and polyethylene-like crystals by simulation with supercomputers have established a link between microscopic motion and macroscopic effect [1-9]. It was shown that conformational, rotational, and diffusional motion can start considerably below the melting or disordering transition temperatures. These types of motion underlie much of the observed macroscopic properties of polymers, and thus it is essential to develop an understanding of how such motion occurs on the microscopic level (mechanisms) and the rates of changes it introduces (kinetics). 

Although the majority of bonds are at any one time close to tram conform-ers , each of them is found to deviate frequently more than expected from normal vibrations. The zig-zag chains often obtain a twist by sequential deviations in the same rotation direction. The formation of such twists is demonstrated in a spatial plot in Fig. 5. A series of time snapshots of the center paraffin chain of the simulated crystal is drawn at 316 K. As can be seen, the chain undergoes rapid... 

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