Calculating free energies for diffusion in tight-fitting zeolite-guest systems: Local normal-mode Monte Carlo

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Journal of Chemical Physics. 2003;118(6512). doi: 10.1063/1.1558033

Calculating free energies for diffusion in tight-fitting zeolite-guest systems: Local normal-mode Monte Carlo Turaga Lab

Turaga Srinivas, Auerbach Scott

Note: Research in this publication was not performed at Janelia.

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Abstract

We present an efficient Monte Carlo algorithm for simulating diffusion in tight-fitting host–guest systems, based on using zeolitenormal modes. Computational efficiency is gained by sampling framework distortions using normal-mode coordinates, and by exploiting the fact that zeolite distortion energies are well approximated by harmonic estimates. Additional savings are obtained by performing local normal-mode analysis, i.e., only including the motions of zeolite atoms close to the jumping molecule, hence focusing the calculation on zeolite distortions relevant to guest diffusion. We performed normal-mode analysis on various silicalite structures to demonstrate the accuracy of the harmonic approximation. We computed free energy surfaces for benzene in silicalite, finding excellent agreement with previous theoretical studies. Our method is found to be orders-of-magnitude faster than comparable Monte Carlo calculations that use conventional forcefields to quantify zeolite distortion energies. For tight-fitting guests, the efficiency of our new method allows flexible-lattice simulations to converge in less CPU time than that required for fixed-lattice simulations, because of the increased likelihood of jumping through a flexible lattice.

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Calculating free energies for diffusion in tight-fitting zeolite-guest systems: Local normal-mode Monte Carlo

Note: Research in this publication was not performed at Janelia.

Abstract

Janelia Authors