Interactions, molecular dynamics with three-body

A. Nakano, P. Vashishta, and R. K. Kalia, Comput. Phys. Commun., 77, 303 (1993). Parallel Multiple-Time-Step in Molecular Dynamics with Three-Body Interaction. 

Molecular Dynamics with Three-Body Interactions... 

Molecular Dynamics Simulations of Simple Fluids with Three-Body Interactions Included... 

Classical molecular dynamics (MD) implementing predetermined potentials, either empirical or derived from independent electronic structure calculations, has been used extensively to investigate condensed-matter systems. An important aspect in any MD simulation is how to describe or approximate the interatomic interactions. Usually, the potentials that describe these interactions are determined a priori and the full interaction is partitioned into two-, three-, and many-body contributions, long- and short-range terms, etc., for which suitable analytical functional forms are devised. Despite the many successes with classical MD, the requirement to devise fixed potentials results in several serious problems... 

Induced dipole autocorrelation functions of three-body systems have not yet been computed from first principles. Such work involves the solution of Schrodinger s equation of three interacting atoms. However, classical and semi-classical methods, especially molecular dynamics calculations, exist which offer some insight into three-body dynamics and interactions. Very useful expressions exist for the three-body spectral moments, with the lowest-order Wigner-Kirkwood quantum corrections which were discussed above. 

Figure 18. Pair correlation function g(r), at T = 297.6 K, for p = 0.95, 1.37, 1.69, and 1.93 nm 3 (from the bottom to the top), calculated by the ODS integral equation with both the two-body interactions (dotted lines), and the two- plus three-body interactions (solid lines). The curves for p= 1.37, 1.69, and 1.93 nm-3 are shifted upward by 0.5, 1, and 1.5, respectively. The comparison is made with molecular dynamics simulation (open circles). Taken from Ref. [129].

Computer simulation of molecular dynamics is concerned with solving numerically the simultaneous equations of motion for a few hundred atoms or molecules that interact via specified potentials. One thus obtains the coordinates and velocities of the ensemble as a function of time that describe the structure and correlations of the sample. If a model of the induced polarizabilities is adopted, the spectral lineshapes can be obtained, often with certain quantum corrections [425,426]. One primary concern is, of course, to account as accurately as possible for the pairwise interactions so that by carefully comparing the calculated with the measured band shapes, new information concerning the effects of irreducible contributions of inter-molecular potential and cluster polarizabilities can be identified eventually. Pioneering work has pointed out significant effects of irreducible long-range forces of the Axilrod-Teller triple-dipole type [10]. Very recently, on the basis of combined computer simulation and experimental CILS studies, claims have been made that irreducible three-body contributions are observable, for example, in dense krypton [221]. 

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