A MOLECULAR-DYNAMICS STUDY OF CHAIN CONFIGURATIONS IN N-ALKANE-LIKE LIQUIDS

We present precise measurements of the configurational properties of n -alkane-like liquids with 4, 5, 8, 20, 50, and 100 methylene groups. Q uantities measured include the distributions of square radii of gyrati on, square end-to-end distances and proportion of conformers. To achie ve high precision for n=50 and 100 a Fujitsu AP 1000 massively paralle l processing machine with up to 512 processors is used. The results ar e compared with those obtained for the Flory model of alkane chains in which only correlation between nearest-neighbor torsion angles are co nsidered; the latter were obtained by Monte Carlo sampling of isolated chains using the pivot algorithm. Discrepancies between the two sets of data are discussed in terms of solvent and end effects. For n=100 f ull configurational relaxation was not observed within 2 ns.