Computational study of the structures and thermodynamic properties of ammonium chloride clusters using a parallel jump-walking approach

Authors: Alexander Matro(*), David L. Freeman(*) and Robert Q. Topper(#)

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The thermodynamic and structural properties of (NH₄Cl)_n clusters, n=3-10 are studied. Using the method of simulated annealing, the geometries of several isomers for each cluster size are examined. Jump-walking Monte Carlo simulations are then used to compute the constant-volume heat capacity for each cluster size over a wide temperature range. To carry out these simulations a new parallel algorithm is developed using the parallel virtual machine (PVM) software package. Features of the cluster potential energy surfaces, such as energy differences among isomers and rotational barriers of the ammonium ions, are found to play important roles in determining the shape of the heat capacity curves.

(*)Department of Chemistry, University of Rhode Island, Kingston, RI.

(#)Department of Chemistry, The Cooper Union for the Advancement of Science and Art, New York, NY.

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