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Klimontovich Yu.L.

Thermodynamic and kinetic description
of the second order phase transitions

Yu.L. Klimontovich
Physical Department, Moscow State University, Russia

The purpose of report - critical analysis of opportunities alternate thermodynamic and kinetic description of phase transitions of the second order in system gas-liquid and in ferroelectrics. On these examples comparison of results of the theory Landau and results of the statistical theory of open systems is conducted.

Introduction contains minimum necessary at an exposition of a main material of the item of information about phase transitions. In a basis of the theory of phase transitions in system gas-liquid the model of Van der Waals is used.

The phase transition in ferroelectrics is simulated by system from bistable elements. The soft mode - negative rigidity results from action of an effective Lorentz field. For the space homogeneous medium two alternate methods of the thermodynamic description of phase transitions of the second order are compared. First answers the theory Landau, when are assumed the existence of the coherent distribution of values of parameter of the order. Second is based on appropriate the Boltzmann distribution. Last lets to describe not only jump, but also peak in the temperature dependence of heat capacity in a vicinity tex2html_wrap_inline3134 - point.

On a basis S - theorem the comparison of a relative degree order for states above and below tex2html_wrap_inline3134 - point is conducted. On this criterion transition from more symmetric to a less symmetric phase is presented as the process of self-organizing.

For model of a ferroelectrics and model of Van der Waals is conducted the kinetic description of fluctuations for of processes at phase transitions of the second order. In particular, the Langevin sources in the Ginzburg- Landau relaxation equation - equation of a reaction-diffusion type, for two contributions - "reactionary" and diffusion are determined. Accounts of appropriate space-temporary spectra of fluctuations are conducted at all temperatures, switching on and the critical point.

The results much differ from received on the basis of the Landau theory with allowance for space-temporary fluctuations. In particular, is shown, that within the framework of the Landau model does not exist space fluctuations of the Dedye-like type.

Availability large-scale space-temporary fluctuations is established also, ensuring existence of the coherent state at temperatures is lower of the critical one.


next up previous
Next: Konukhov A.I.Melnikov L.A., Ryabinina M.V. Up: Book of Abstracts Previous: Kipchatov A.A. and Podin S.V.

Book of abstracts
ICND-96