Theoretical and Numerical Analysis of a Locally Nonchaotic Energy Barrier

In the current research, we investigate a billiard-type model system, in which elastic particles randomly move across a locally nonchaotic energy barrier between an upper plateau and a lower plain. The energy barrier is a type of spontaneously nonequilibrium dimension. Its size is much smaller than the mean free path of the particles; it leads to a non-Boltzmann steady-state particle distribution, without any specific knowledge of the system microstate.

The second law of thermodynamics dictates that the particles must follow the Maxwell-Boltzmann distribution; otherwise, useful work may be produced in a cycle by absorbing heat from a single thermal reservoir. However, our Monte Carlo simulation confirms that the particle distribution is indeed nonequilibrium. Without extensive particle collision in the transition step, there is no mechanism for the system to reach thermodynamic equilibrium. Consequently, in an isothermal cycle, the produced work is greater than the consumed work.   

We show that such an anomalous phenomenon, although counterintuitive, strictly follows the basic principle of thermodynamics. It can be attributed to the asymmetry in the cross-influence of thermally correlated thermodynamic driving forces. There are a number of variants that can have similar effects, e.g., when the plateau-plain boundary is asymmetric or switchable.