Improved Force-Field Parameters for QM/MM Simulations of the Energies of Adsorption for Molecules in Zeolites and a Free Rotor Correction to the Rigid Rotor Harmonic Oscillator Model for Adsorption Enthalpies

Yi-Pei Li; Joseph Gomes; Shaama Mallikarjun Sharada; Alexis T Bell; Martin Head-Gordon

doi:10.1021/jp509921r

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Improved Force-Field Parameters for QM/MM Simulations of the Energies of Adsorption for Molecules in Zeolites and a Free Rotor Correction to the Rigid Rotor Harmonic Oscillator Model for Adsorption Enthalpies

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Improved Force-Field Parameters for QM/MM Simulations of the Energies of Adsorption for Molecules in Zeolites and a Free Rotor Correction to the Rigid Rotor Harmonic Oscillator Model for Adsorption Enthalpies

Yi-Pei Li, Joseph Gomes, Shaama Mallikarjun Sharada, Alexis T Bell and Martin Head-Gordon

Journal of physical chemistry. C, Vol.119(4), pp.1840-1850

01/29/2015

DOI: 10.1021/jp509921r

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Abstract

Quantum mechanics/molecular mechanics (QM/MM) simulations provide an efficient avenue for studying reactions catalyzed in zeolite systems; however, the accuracy of such calculations is highly dependent on the zeolite MM parameters used. Previously reported parameters (P1), which were chosen to minimize the root mean square (RMS) deviations of adsorption energies compared with full QM ωB97X-D/6-31+G** adsorption energies, are shown to overestimate binding energies compared with experimental values, particularly for larger substrates. To address this issue, a new parameter set (P2) is derived by rescaling the previously reported characteristic energies of the Lennard-Jones potential in P1. The accuracy of the thermal correction for adsorption enthalpies determined by the rigid rotor-harmonic oscillator approximation (RRHO) is examined and shown to be improved by treating low-lying vibrational modes as free translational and rotational modes via a quasi-RRHO model. With P2 and quasi-RRHO, adsorption energies calculated with QM/MM agree with experimental values with an RMS error of 1.8 kcal/mol for both nonpolar and polar molecules adsorbed in MFI, H-MFI, and H-BEA. By contrast, the RMS error for the same test sets obtained using parameter set P1 is 8.3 kcal/mol. Glucose–fructose isomerization catalyzed by Sn-BEA is taken as an example to demonstrate that improved values for apparent activation energies can be obtained using the methodology reported here. With parameter set P2, the apparent activation energy calculated with QM/MM reproduces the experimental value to within 1 kcal/mol. By contrast, using parameter set P1, the error is −12.9 kcal/mol.

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Title: Subtitle: Improved Force-Field Parameters for QM/MM Simulations of the Energies of Adsorption for Molecules in Zeolites and a Free Rotor Correction to the Rigid Rotor Harmonic Oscillator Model for Adsorption Enthalpies
Creators: Yi-Pei Li - University of California, Berkeley
Joseph Gomes - University of California, Berkeley
Shaama Mallikarjun Sharada - University of California, Berkeley
Alexis T Bell - University of California, Berkeley
Martin Head-Gordon - University of California, Berkeley
Resource Type: Journal article
Publication Details: Journal of physical chemistry. C, Vol.119(4), pp.1840-1850
DOI: 10.1021/jp509921r
NLM abbreviation: J Phys Chem C Nanomater Interfaces
ISSN: 1932-7447
eISSN: 1932-7455
Publisher: American Chemical Society
Grant note: DOI: 10.13039/100000001, name: National Science Foundation; name: BP plc
Language: English
Date published: 01/29/2015
Academic Unit: Chemical and Biochemical Engineering
Record Identifier: 9984197355202771

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