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Increase in visible order can be associated with an increase in microscopic disorder. This phenomenon leads to many counter-intuitive phenomena such as entropy driven crystallization and phase separation. I devote special attention to the entropic depletion interaction as a means to tune the range of attraction between colloids. The range of the intermolecular potential determines whether or not stable liquid-vapor coexistence is possible. For short range attraction, the liquid-vapor transition may be located below the sublimation line. Under those conditions, meta-stable critical fluctuations may enhance the rate of crystal nucleation
This paper report absolute free-energy calculations of the fluid, body-centered-cubic, and face-centered-cubic phases of helium at T=327.04 K. We find that at and around this temperature the model potential proposed by Aziz et al. doe not yield a stable bcc phase. Quantum corrections do not alter this conclusion
The results of recent computer simulations on fluids of nonspherical hard-core particles are discussed. New data are presented on the structure and dynamics of a system of hard spherocylinders with length-to-width ratio LID = 5. These data show that such spherocylinders can occur in at least four stable phases, viz., isotropic fluid, nematic liquid crystal, crystalline solid, and, surprisingly, a smectic A phase.
We present Monte Carlo simulations of the hopping motion of a particle in a two-dimensional square lattice Lorentz gas. The long time tail of the velocity autocorrelation function in this system is computed with an accuracy of 1:5X105. At low densities the Monte Carlo results agree quantitatively at all times with the predictions of kinetic theory. The theoretical predictions for the second order density corrections to the diffusion constant and the asymptotic behavior of the velocity autocorrelation function are found to be compatible with the Monte Carlo results. To our knowledge, this is the first example of quantitative agreement between kinetic theory and computer simulation for the long time tail of the velocity ACF in a Lorentz gas.
Since the work of Onsager, systems of hard spherocylinders have played a special role as the theoretician’s “ideal” nematic liquid crystals. It is, however, well-known that the Onsager theory is only a good description for extremely nonspherical particles. A quantitative measure for the range of validity of this theory is obtained from direct numerical calculation of the third through fifth virial coefficients of hard spherocylinders with length-to-width ratios, LID, between 1 and lo6. The phase diagram of spherocylinders with “realistic” LID ratios can only be obtained by computer simulation. We report molecular dynamics and Monte Carlo simulations for spherocylinders with LID = 5. These calculations suggest that the oldest model for a hard-core nematic may, in fact, have a smectic liquid-crygalline phase as well. Includes an erratum...
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