Home

About

Advanced Search

Browse by Discipline

Scientific Societies

E-print Alerts

Add E-prints

E-print Network
FAQHELPSITE MAPCONTACT US


  Advanced Search  

 
Simulating the Relaxation Dynamics of Microwave-Driven Zeolites Aldo F. Combariza, Ethan Sullivan, Scott M. Auerbach,*,, and Cristian Blanco,
 

Summary: Simulating the Relaxation Dynamics of Microwave-Driven Zeolites
Aldo F. Combariza, Ethan Sullivan, Scott M. Auerbach,*,, and Cristian Blanco,
Department of Chemistry and Department of Chemical Engineering, UniVersity of Massachusetts,
Amherst, Massachusetts 01003, and Department of Chemistry, UniVersidad Industrial de Santander,
AA 678 Bucaramanga, Colombia
ReceiVed: May 11, 2005; In Final Form: August 2, 2005
We have performed equilibrium and nonequilibrium molecular dynamics simulations to study how microwave
(MW)-heated zeolite systems relax to thermal equilibrium. We have simulated the relaxation of both ionic
and dipolar phases in FAU-type zeolites, finding biexponential relaxation in all cases studied. Fast-decay
times were uniformly below 1 ps, while slow-decay times were found to be as long as 14 ps. Fast-decay
times increase with an increase in the initial temperature difference between MW-heated ions/dipoles and the
equilibrium system. Slow-decay times were found to be relatively insensitive to the details of the MW-
heated nonequilibrium state. Velocity, force, and orientational correlation functions, calculated at equilibrium
to explore the natural dynamics of energy transfer, decay well before 1 ps and show little evidence of
biexponential decay. In contrast, kinetic energy correlation functions show strong biexponential behavior
with slow-decay times as long as 14 ps. We suggest a two-step mechanism involving initial, efficient energy
transfer mediated by strongly anharmonic zeolite-guest forces, followed by a slower process mediated by
weakly anharmonic couplings among normal modes of the zeolite framework. In addition to elucidating
relaxation from MW-heated states, we expect that these studies will shed light on energy transfer in other
contexts, such as adsorption and reaction in zeolites, which often involve significant heat release.

  

Source: Auerbach, Scott M. - Department of Chemistry, University of Massachusetts at Amherst

 

Collections: Chemistry