A contact cavity-biased method for grand canonical Monte Carlo simulations

A modification of the cavity-biased grand canonical Monte Carlo (GCMC) proposed by Mezei is introduced here. Instead of on a fixed grid, test points of cavities are generated at the contact positions around the centers of existing particles. The increase in the probability or bias of finding a cavity is related to the radial distribution function and can hence be corrected. With this new cavity-biased implementation, an improved convergence to equihbrium is demonstrated and higher densities can be attained. Comparisons with the standard GCMC method, and the original cavity-biased scheme of Mezei are made. © 1994 American Institute of Physics.published_or_final_versio

Contact values for disparate-size hard-sphere mixtures

A universality ansatz for the contact values of a multicomponent mixture of additive hard spheres is used to propose new formulae for the case of disparate-size binary mixtures. A comparison with simulation data and with a recent proposal by Alawneh and Henderson for binary mixtures shows reasonably good agreement with the predictions for the contact values of the large-large radial distribution functions. A discussion on the usefulness and limitations of the new proposals is also presented.Comment: 12 pages, 10 figures; v2: typo in Eq. (28) correcte

A further test of the Boublik et al. equations for binary hard sphere mixtures

The Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) equation of state is examined for binary hard sphere mixtures. It is argued that this equation of state is reliable for a large diameter ratio. Monte Carlo (MC) simulations are performed for many states, some of high density and large diameter ratio. At moderate densities away from the solid-liquid transition, the MC results show reasonably good agreement with the BMCSL's prediction of the compressibility factor. This confirms the earlier findings of Jackson et al. for the validity of BMCSL in the liquid phase. The failure of the BMCSL prediction in some states is due to proximity to the solid-liquid transition and not due to the large diameter ratio. The individual pair distribution functions predicted by the BMCSL in all cases, however, can be poor, especially, for a pair of large spheres at very low concentration. Comparison of the MC distribution functions and those predicted by several theories are made.link_to_subscribed_fulltex

Pair correlation functions for a hard sphere mixture in the colloidal limit

Previously, we have proposed an approximation for the contact values of the radial distribution functions of a hard sphere mixture. For most situations, this approximation is similar to earlier approximations. However, our approximation is quite different in the colloidal limit, where one species is large in size but whose concentration is very dilute. We called this approximation the ad hoc approximation to emphasize that this new approximation was untested. In this paper, we seek to test this ad hoc approximation by computing, by means of a Monte Carlo simulation, the pair correlation functions for a binary hard sphere mixture. We are able to consider mixtures in which the large hard sphere is up to 10 times the size of the small hard sphere and concentrations of the large sphere as small as 1%. While not the colloidal limit, these results are informative. The ad hoc approximation is found to be in good agreement with the simulation results.link_to_subscribed_fulltex

Formation of Al2Cu and AlCu intermetallics in Al(Cu) alloy matrix composites by reaction sintering

We report the fabrication and characterization of a series of Al(Cu) alloy-based matrix composites. The composites were produced by sintering and rapid quenching three powder mixtures of Al and Cu with hypoeutectic, eutectic, and hypereutectic compositions. The morphology of the reinforcements formed in the Al(Cu) matrices of these composites was found to be variable. A two-phase Al2Cu-Al(Cu) nanoeutectic, with lamellar spacing of 200-300 nm, was found in the Al(Cu) matrix of the sample having hypoeutectic composition after it was oil-quenched from 1000 degreesC to room temperature. While oil quenching the sample with eutectic composition, produced single Al2Cu Crystals of 2-2.5 mum size, embedded in a lamellar nanoeutectic matrix. As for the hypereutectic alloy, the matrix of the oil-quenched sample consisted mainly of Al2Cu intermetallic, and a secondary phase of AlCu dendrites with dendrite arms spacing of 1-1.5 mum. (C) 2004 Elsevier B.V All rights reserved

Formation of micron-sized and nanometer-sized single crystal alumina whiskers by displacement reactions

We propose a general methodology for fabricating single crystal alpha-Al2O3 whiskers by displacement reactions. The methodology is based on studies in which Al-rich powder mixtures that contain different kinds of metal oxides (MOx) were sintered. In some sintered products, the in situ formed Al2O3 appeared as particulate while in other it appeared as whiskers. Some conclusions from this study are: growth of the whiskers involves the presence of MOx-1 vapor and Al2O vapor during sintering, and the dimension of the whiskers depends oil the size of the initial MO., particles. Micron-sized whiskers were produced in Al-MoO3 and in Al-WO3, while nanorods were produced ill Al-SiO2. (c) 2005 Elsevier Ltd. All rights reserved