Dresden 2017 – scientific programme

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BP: Fachverband Biologische Physik

BP 15: Colloids and Complex Fluids I (Joint Session CPP/BP/DY)

BP 15.6: Talk

Tuesday, March 21, 2017, 12:45–13:00, ZEU 255

Phonons and Elasticity in Disordered binary Crystals — •Tadeus Ras and Matthias Fuchs — FB Physik, Univ. Konstanz

The “method of long waves” is a well-established tool for the study of elastic constants [1]. However, until recently, it had been lacking in crystals with point defects due to an unclear definition of the displacement field.

We present a generalization of the projection-operator approach employed in [2]. It yields expressions for the elastic constants valid in binary crystals with arbitrary amounts of point defects and up to the melting temperature. Further, both acoustic and optical phonon eigenfrequencies can be computed in linear response.

While density functionals from classical DFT serve as an input parameter to the approach it can also be employed experimentally to process measurement data. For demonstration, dispersion relations will be shown as obtained from molecular dynamics data of a hard sphere model crystal [3].
D. C. Wallace, Thermodynamics of Crystals (Wiley, NY 1972).
C. Walz and M. Fuchs, Phys. Rev. B 81, 134110 (2010).
L. Filion et. al., Phys. Rev. Lett. 107, 168302 (2011).