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17Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2016
PHASE TRANSITIONS AND DYNAMICAL ENTROPY IN SMALL DUST CLUSTERS SUSPENDED IN GAS-DISCHARGE PLASMA
X.G. Koss, OF. Petrov, M.I. Myasnikov, KB. Statsenko, MM. Vasiliev
JIHTRAS, Moscow, Russia, e-mail: ofpetrov@ihed.ras.ru
During last decade, the study of small systems of interacting particles became a relevant topic in various fields of science and technology, including nanoengineering and materials design. The question of dynamics of these structures becomes even more intriguing as far as open dissipative systems are concerned, as the theory of nonequilibrium phase transitions greatly differs from the description of equilibrium ones.
The methods of analysis of dynamical systems are the most illustrative and convenient to study these systems. We use the concept of the "dynamic entropy" [1, 2] in its simple approach called "mean first-passage time" (MFPT) dynamic entropy [3] to study numerically and experimentally obtained small systems of interacting particles.
The experiments were carried out in the quasi-two-dimensional system of dust grains in gas discharge plasma. Thanks to their high electrical charge (10A3-10A4 e), the system of 7 grains levitated above the lower electrode, forming a cluster confined by an external electrical field. This system was simulated with the help of Langevin molecular dynamics method. The interparticle interaction potential was taken to be of Yukawa type; for the details see [4].
We have obtained the MFPT entropy functions for the systems under study and analyzed them to find out their phase states. Three phase states of the considered small systems are registered: crystal, liquid and transitional. The character of motion for different states was examined using the functions of dependence of mean-square displacement of particles on time.
The suggested technique of the analysis of the system dynamics can be applied to the structures as small as desired, independent on the degree of the thermal isolation of the system. This work was supported by the Russian Science Foundation (project No 14-12-01440).
References
1. C. E. Shannon, Bell Syst. Tech. J. 27, 379 (1948); 27, 623 (1948)
2. A. N. Kolmogorov, Dokl. Acad. Sci. USSR 124, 754 (1959); Y. G. Sinai, ibid. 124, 768 (1959).
3. P. Allegrini, J. F. Douglas, and S. C. Glotzer, PRE 60, 5714 (1999)
4. Complex and Dusty Plasmas, ed. by V. E. Fortov and G. E. Morfill, CRC Press, (2010)
