Cristian Blanco and Scott M. Auerbach, ``Simulating Non-Equilibrium Dynamics in Nanopores: Microwave-Heated Diffusion of Methanol and Benzene in DAY Zeolite,'' J. Comput. Theor. Nanosci. 1, 183-189 (2004).

Abstract

We have performed equilibrium molecular dynamics and microwave (MW) heated molecular dynamics simulations to explore how MW heating influences self-diffusion in zeolite nanopores. We have applied these simulations to methanol and/or benzene in de-aluminated Y zeolite. We find that even under the non-equilibrium conditions of MW heating, center-of-mass motions can be associated with effective temperatures. However, we find that the temperatures controlling kinetic and potential energy distributions are not generally the same in MW-heated systems, with potential temperatures generally exceeding kinetic ones. This finding has a consequence for understanding MW-heated diffusion in zeolites. In particular, when temperatures are sufficiently high that diffusion is not strongly activated, MW-heated diffusivities are equal to equilibrium diffusivities at the same kinetic temperature. On the other hand, when diffusion becomes more strongly activated at lower temperatures, MW-heated diffusivities consistently exceed equilibrium diffusivities at the same kinetic temperature, because the MW-heated potential distributions enable more facile barrier crossing. This result shows that in general, MW-heated diffusion is more complicated than simply ``different components diffusing at different temperatures.'' Instead, we advocate the picture involving different components diffusing at different kinetic and potential temperatures.

Prof SM Auerbach
19 March 2004