Regensburg 2004 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 28: Glasses I (joint session DF/DY)

DY 28.2: Vortrag

Dienstag, 9. März 2004, 10:15–10:30, H23

Mode coupling equations for molecular crystals — •Michael Ricker und Rolf Schilling — Universität Mainz, Staudinger Weg 7, 55099 Mainz

We have derived the mode coupling equations for molecular crystals of axially symmetric particles, describing the time evolution of the tensorial orientational correlators S_lm,l′m′(q,t), where lm and l′m′ are pairs of indices for spherical harmonics. These equations have a similar structure as those for molecular liquids. Differences arise from the possibility of umklapp-processes in reciprocal space and from the anisotropy of the lattice. Because of the latter, the three-point correlation function of orientational density fluctuations, which occurs due to projections during the calculations, can not be approximated in such an elegant and insightful way as for liquid systems. Another difference is that only tensorial orientational correlators with l,l′ > 0 are involved, since the l = 0 and/or l′=0 correlators vanish.

If these mode coupling equations can describe the formation of orientational glasses is currently tested for hard ellipsoids of revolution on a simple cubic lattice. The static orientational structure factors S_lm,l′m′(q), which are needed as input, are taken from MC simulations and from the solution of the Ornstein-Zernike equation using the Percus-Yevick approximation.