SEMICLASSICAL MOLECULAR-DYNAMICS SIMULATIONS OF LOW-TEMPERATURE CLUSTERS - APPLICATIONS TO (AR)(13), (NE)(13), (H2O)(N), N=2,3,5

Semiclassical molecular dynamics simulations are developed as a tool f or studying anharmonic clusters and solids at energies near the zero p oint. The method employs the time-dependent self-consistent-held appro ximation, that describes each mode as moving in the mean dynamical fie ld of all other modes. The method further describes each mode by a sem iclassical Gaussian wave packet; The scheme is carried out in normal m odes. The method is restricted to systems of moderate anharmonicity at low temperatures. It is, however, computationally efficient and pract ically applicable to large systems. It can be used for the dynamics of nonstationary states as well as for stationary ones. Structural, dyna mical and a variety of spectroscopic properties can easily be evaluate d. The method is tested for thermal equilibrium states of (Ne)(13), (A r)(13) against ''numerically exact'' quantum Feynman path integral sim ulations. Excellent quantitative agreement is found for the atom-atom pair distribution functions. The method is also applied to (H2O)(n) cl usters. Good agreement is found with experimentally available fundamen tal stretch-mode frequencies. (C) 1996 American Institute of Physics.