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New clues on the thermodynamic behaviour in small systems

04 February 2014 Universidad de Barcelona

The energy lost in small systems, like nanodevices, can be decisive in order to obtain an optimal functioning of this kind of systems. Under a thermodynamic point of view, the application of the stability theory and classical statistical mechanics to the description of small systems under destabilizing external conditions reveals a constant generation of heat while the system oscillates between two structural configurations or thermodynamic phases. 

A research published on the journal Physical Review E, and signed by Agustín Pérez, from the Department of Fundamental Physics of the University of Barcelona, and Iván Santamaría, from the National Autonomous University of Mexico, analyses the implications of the finite size of the system on its thermodynamic behaviour.

“The results obtained in this research are of great interest since they underlie the physics of the energy generation and conversion nanodevices. Potential applications have been recently reported for energy nano-generators, systems based on the pyroelectric effect, and electric energy storage systems like batteries”, explains Agustín Pérez.

When a macroscopic system is subjected to destabilizing conditions, it separates into two or more phases that may coexist in equilibrium. This involves the formation of interfaces and, finally, new thermodynamic systems emerge. 

However, when the system is finite and small enough, like nanodevices, the formation of an interface could imply an excessively high energetic cost and, therefore, becomes energetically unfavourable. Thus, this system will remain in a stationary state strongly sensitive to fluctuations. Nevertheless, since the thermodynamic parameters of both states differ from those of the external bath, a thermodynamic force known as critical oscillation appears driving the state of the system towards the unstable state externally imposed were again it cannot remain. “As a result of this description, it can be predicted that this peculiar behaviour of small systems underlie the dynamic of energy generating, storage or conversion nanodevices”, Pérez concludes.

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