Plastic Crystals

In plastic crystals the centers of mass of the molecules form a regular crystalline lattice but the molecules are dynamically disordered with respect to the orientational degrees of freedom (see figure below). Orientationally disordered crystals are often considered as model systems for structural glasses. It is our aim to investigate the relaxation dynamics focusing on the high-frequency behavior also in this totally different class of glass forming systems.

Amongst others, the investigations in our group include the following materials (click on the names to learn more):

An overview of our investigations on various plastic crystals can be found in:

Relaxation dynamics in plastic crystals
R. Brand, P. Lunkenheimer, and A. Loidl
J. Chem. Phys. 116, 10386 (2002).

structural glass formers vs. plastic crystals

Some relevant publications from our group:

(click here for a complete list of publications of our group)

Relaxation and Fast Dynamics of the Plastic Crystal Cyclo-octanol Investigated by Broadband Dielectric Spectroscopy
R. Brand, P. Lunkenheimer, and A. Loidl
Phys. Rev. B 56, R5713 (1997).
Excess wing and high-frequency dynamics in plastic crystals
P. Lunkenheimer, R. Brand, U. Schneider, and A. Loidl
Phil. Mag. B 79, 1945 (1999).
High Frequency Dielectric Response of Plastic Crystals
P. Lunkenheimer, R. Brand, U. Schneider, and A. Loidl
Proceedings of the 8th Tohwa University International Symposium Fukuoka "Slow Dynamics in Complex Systems" (AIP Conference Proceedings, 1999); 469, p. 671-672.
Is there an Excess Wing in the Dielectric Loss of Plastic Crystals
R. Brand, P. Lunkenheimer, U. Schneider, and A. Loidl
Phys. Rev. Lett. 82, 1951 (1999).
Scaling of broadband dielectric data of glass-forming liquids and plastic crystals
U. Schneider, R. Brand, P. Lunkenheimer, and A. Loidl
Eur. Phys. J. E 2, 67 (2000).
Relaxation dynamics in plastic crystals
R. Brand, P. Lunkenheimer, and A. Loidl
J. Chem. Phys. 116, 10386 (2002).
α- and β-relaxation dynamics of a fragile plastic crystal
L.C. Pardo, P. Lunkenheimer, and A. Loidl
J. Chem. Phys. 124, 124911 (2006).
High-frequency excitations in glassy crystals
P. Lunkenheimer and A. Loidl
J. Non-Cryst. Solids 352, 4556 (2006).
New microscopic mechanism for secondary relaxation in glasses
M. Zuriaga, L.C. Pardo, P. Lunkenheimer, J.Ll. Tamarit, N. Veglio, M. Barrio, F.J. Bermejo, and A. Loidl
Phys. Rev. Lett. 103, 075701 (2009).
Relaxation dynamics and ionic conductivity in a fragile plastic crystal
Th. Bauer, M. Köhler, P. Lunkenheimer, A. Loidl, and C.A. Angell
J. Chem. Phys. 133, 144509 (2010).

For further information please contact:
peter.lunkenheimer@physik.uni-augsburg.de

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Some relevant publications from our group: