Browsing by Author "Gregory, Victor Paul"

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    Monte Carlo computer simulation of sub-critical Lennard-Jones particles
    Gregory, Victor Paul (Virginia Tech, 1991-03-05)
    Cluster characteristics of the 3D Lennard-Jones, LJ, fluid are determined by Metropolis Monte Carlo computer simulations. The percolation probability and cluster distribution is calculated for several state points in the gas-liquid equilibrium region of the LJ fluid. The cluster number distribution is used to analyze the distribution of clusters above and below the percolation threshold. Using scaling theory, the critical exponent, Ï , is determined from the cluster distributions. Deviation from the scaling law is evaluated using a modified scaling law that includes a surface term. It is found that the surface term is unnecessary in the gas-like area of the phase diagram. The density profiles of large non-percolating clusters are calculated in order to study the surface structure of the clusters. The coordination number within a cluster is calculated directly in the simulation and, with the cluster energy, is used to discern the amount of "liquid-like" structure of the cluster. The radius of gyration, R g, as a function of cluster size determines the fractal dimension, D f of the non-percolating and clusters above and below the percolation threshold density. Finite size effects are briefly studied and presented for a few of points.
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    Monte Carlo computer simulation of the Lennard-Jones and Stockmayer fluid phase diagrams
    Gregory, Victor Paul (Virginia Tech, 1994-02-05)
    The isotherms of the Lennard-Jones fluid and the Stockmayer fluid are calculated by Monte Carlo computer simulation using the constant NpT ensemble. Empirical coefficients are determined for a truncated virial equation of state fitted to our data. Spinodal points are located for each temperature and fluid. For temperatures less than 0.90 of the critical temperature, we succeeded in temporarily isolating clusters during the gas to liquid transition for the LJ fluid. Density profiles are calculated for clusters at and above the spinodal pressures. The clusters above the spinodal pressure have liquid-like densities at their centers and are identified as critical condensation clusters. The clusters at the spinodal increase in size with temperature and have densities roughly half as dense as the equilibrium liquid at their centers. It is found that the results are essentially system size independent.