Eur. Phys. J. B 44, 509-519 (2005)
https://doi.org/10.1140/epjb/e2005-00151-2

Thermodynamics and phase transitions in dissipative and active Morse chains

¹ Faculty of Nonlinear Processes, Saratov State University, Astrakhanskaya 83, 410012 Saratov, Russia
² Institut für Physik, Humboldt-Universität Berlin, Newtonstrasse 15, 12489 Berlin, Germany
³ Instituto Pluridisciplinar, Universidad Complutense, Paseo Juan XXIII, 1, 28040 Madrid, Spain

Corresponding author: ^a ebeling@physik.hu-berlin.de

Received: 10 August 2004
Revised: 27 January 2005
Published online: 30 May 2005

Abstract

We study the evolution of a simple one-dimensional chain of N=4 particles with Morse interactions and periodic boundary conditions which are imbedded into a heat bath creating dissipation and noise. The investigation is concentrated on thermodynamic properties for equilibrium, near-equilibrium and far-equilibrium conditions. For the thermodynamic equilibrium, created by white noise and passive friction obeying Einstein's fluctuation dissipation relation, we find a standard phase diagram. By applying active friction forces the system is driven to stationary non-equilibrium states, creating conditions where various self-sustained oscillations are excited. Thermodynamic quantities like energy, pressure and entropy are calculated near equilibrium, around a critical distance from equilibrium and far from equilibrium. We observe maximal order (minimum entropy) in certain region of the noise temperature, a phenomenon which is reminiscent of stochastic resonance. With increasing distance from equilibrium new “phases” corresponding to the existence of several attractors of the dynamical stem appear.