화학공학소재연구정보센터
Journal of Chemical Physics, Vol.110, No.9, 4523-4532, 1999
A path integral centroid molecular dynamics study of nonsuperfluid liquid helium-4
Path integral centroid molecular dynamics (CMD) calculation for normal liquid He-4 has been performed. Dynamical behavior of the liquid at 4 K, which can not be reproduced by classical approximation, was well described by the CMD formalism. The calculated self-diffusion coefficient was found to be 5.06 +/-0.04 x 10(-5) cm(2)/s, which is in the same order of magnitude as that of ordinary liquids. Relaxation function of density fluctuation has also been calculated within the CMD approximation. Detailed comparison between the static susceptibility function <(chi)over cap>(k) and the static structure factor of the centroid density (S) over cap((c))(k) has been made. These correspond to the initial value of the exact and the centroid relaxation functions, respectively. For small k (less than or equal to 1.0 Angstrom(-1)), <(chi)over cap>(k) is well approximated by (S) over cap((c))(k). For larger k, both the correlation functions have identical peak position. However, the intensity of (S) over cap((c))(k) is systematically larger than that of <(chi)over cap>(k). The calculated dynamic structure factor has been compared with the spectrum obtained from neutron scattering experiment. The agreement is satisfactory for 0.2