Berlin 2015 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 56: Poster - Statistical Physics

DY 56.10: Poster

Thursday, March 19, 2015, 16:00–18:00, Poster A

Deriving elasticity theory for non-ideal crystals: application to cluster crystals — •Johannes Häring, Matthias Fuchs, and Christof Walz — Universität Konstanz, 78457 Konstanz

For non-ideal crystals density fluctuations can be expressed by deformations of the underlying lattice structure plus changes in the occupancy of the single lattice sites. In our approach these density variations from a equilibrium density play the role of the displacement from the equilibrium position in normal elasticity theory.

Through classical density functional theory it is possible to obtain the hydrodynamic equations of motion, a wave equation , expressions for the constants of elasticity and the isothermal compressibility.

A well-known model for cluster crystals, the so called generalized exponential model is used to demonstrate the capability of the theory because its big differences in occupancy of each lattice site (e.g. fluctuations from 12 to 15 particles per lattice site) lead to a significant deviation from the ideal crystal.