Dynamic Charge Equilibration-morse stretch force field

application to energetics of pure silica zeolites

J Sefcik, E Demiralp, T Cagin, W A Goddard

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

We present the Dynamic Charge Equilibration (DQEq) method for a self-consistent treatment of charge transfer in force field modeling, where atomic charges are designed to reproduce electrostatic potentials calculated quantum mechanically. Force fields coupled with DQEq allow charges to readjust as geometry changes in classical simulations, using appropriate algorithms for periodic boundary conditions. The full electrostatic energy functional is used to derive the corresponding forces and the second derivatives (hessian) for vibrational calculations. Using DQEq electrostatics, we develop a simple nonbond force field for simulation of silica molecular sieves, where nonelectrostatic interactions are described by two-body Morse stretch terms. Energy minimization calculations with the new force field yield accurate unit cell geometries for siliceous zeolites. Relative enthalpies with respect to quartz and third-law entropies calculated from harmonic vibrational analysis agree very well with available calorimetric data: calculated SiO2 enthalpies relative to a-quartz are within, 2 kJ/mol and entropies at 298 K are within 3 Ymol K of the respective experimental values. Contributions from the zero point energy and vibrational degrees of freedom were found to be only about I kJ/mol for the free energy of mutual transformations between microporous silica polymorphs. The approach presented here can be applied to interfaces and other oxides as well and it is suitable for development of force fields for accurate modeling of geometry and energetics of microporous and mesoporous materials, while providing a realistic description of electrostatic fields near surfaces and inside pores of adsorbents and catalysts.

Original languageEnglish
Pages (from-to)1507-1514
Number of pages8
JournalJournal of Computational Chemistry
Volume23
Issue number16
Early online date9 Oct 2002
DOIs
Publication statusPublished - Dec 2002

Fingerprint

Zeolites
Force Field
Stretch
Silica
Silicon Dioxide
Electrostatics
Quartz
Charge
Geometry
Enthalpy
Entropy
Microporous materials
Mesoporous materials
Molecular sieves
Polymorphism
Adsorbents
Oxides
Free energy
Charge transfer
Electrostatic Field

Keywords

  • force field modeling
  • silica zeolites
  • dynamic charge equilibration

Cite this

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title = "Dynamic Charge Equilibration-morse stretch force field: application to energetics of pure silica zeolites",
abstract = "We present the Dynamic Charge Equilibration (DQEq) method for a self-consistent treatment of charge transfer in force field modeling, where atomic charges are designed to reproduce electrostatic potentials calculated quantum mechanically. Force fields coupled with DQEq allow charges to readjust as geometry changes in classical simulations, using appropriate algorithms for periodic boundary conditions. The full electrostatic energy functional is used to derive the corresponding forces and the second derivatives (hessian) for vibrational calculations. Using DQEq electrostatics, we develop a simple nonbond force field for simulation of silica molecular sieves, where nonelectrostatic interactions are described by two-body Morse stretch terms. Energy minimization calculations with the new force field yield accurate unit cell geometries for siliceous zeolites. Relative enthalpies with respect to quartz and third-law entropies calculated from harmonic vibrational analysis agree very well with available calorimetric data: calculated SiO2 enthalpies relative to a-quartz are within, 2 kJ/mol and entropies at 298 K are within 3 Ymol K of the respective experimental values. Contributions from the zero point energy and vibrational degrees of freedom were found to be only about I kJ/mol for the free energy of mutual transformations between microporous silica polymorphs. The approach presented here can be applied to interfaces and other oxides as well and it is suitable for development of force fields for accurate modeling of geometry and energetics of microporous and mesoporous materials, while providing a realistic description of electrostatic fields near surfaces and inside pores of adsorbents and catalysts.",
keywords = "force field modeling, silica zeolites, dynamic charge equilibration",
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Dynamic Charge Equilibration-morse stretch force field : application to energetics of pure silica zeolites. / Sefcik, J ; Demiralp, E ; Cagin, T ; Goddard, W A .

In: Journal of Computational Chemistry , Vol. 23, No. 16, 12.2002, p. 1507-1514.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Dynamic Charge Equilibration-morse stretch force field

T2 - application to energetics of pure silica zeolites

AU - Sefcik, J

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AU - Cagin, T

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N2 - We present the Dynamic Charge Equilibration (DQEq) method for a self-consistent treatment of charge transfer in force field modeling, where atomic charges are designed to reproduce electrostatic potentials calculated quantum mechanically. Force fields coupled with DQEq allow charges to readjust as geometry changes in classical simulations, using appropriate algorithms for periodic boundary conditions. The full electrostatic energy functional is used to derive the corresponding forces and the second derivatives (hessian) for vibrational calculations. Using DQEq electrostatics, we develop a simple nonbond force field for simulation of silica molecular sieves, where nonelectrostatic interactions are described by two-body Morse stretch terms. Energy minimization calculations with the new force field yield accurate unit cell geometries for siliceous zeolites. Relative enthalpies with respect to quartz and third-law entropies calculated from harmonic vibrational analysis agree very well with available calorimetric data: calculated SiO2 enthalpies relative to a-quartz are within, 2 kJ/mol and entropies at 298 K are within 3 Ymol K of the respective experimental values. Contributions from the zero point energy and vibrational degrees of freedom were found to be only about I kJ/mol for the free energy of mutual transformations between microporous silica polymorphs. The approach presented here can be applied to interfaces and other oxides as well and it is suitable for development of force fields for accurate modeling of geometry and energetics of microporous and mesoporous materials, while providing a realistic description of electrostatic fields near surfaces and inside pores of adsorbents and catalysts.

AB - We present the Dynamic Charge Equilibration (DQEq) method for a self-consistent treatment of charge transfer in force field modeling, where atomic charges are designed to reproduce electrostatic potentials calculated quantum mechanically. Force fields coupled with DQEq allow charges to readjust as geometry changes in classical simulations, using appropriate algorithms for periodic boundary conditions. The full electrostatic energy functional is used to derive the corresponding forces and the second derivatives (hessian) for vibrational calculations. Using DQEq electrostatics, we develop a simple nonbond force field for simulation of silica molecular sieves, where nonelectrostatic interactions are described by two-body Morse stretch terms. Energy minimization calculations with the new force field yield accurate unit cell geometries for siliceous zeolites. Relative enthalpies with respect to quartz and third-law entropies calculated from harmonic vibrational analysis agree very well with available calorimetric data: calculated SiO2 enthalpies relative to a-quartz are within, 2 kJ/mol and entropies at 298 K are within 3 Ymol K of the respective experimental values. Contributions from the zero point energy and vibrational degrees of freedom were found to be only about I kJ/mol for the free energy of mutual transformations between microporous silica polymorphs. The approach presented here can be applied to interfaces and other oxides as well and it is suitable for development of force fields for accurate modeling of geometry and energetics of microporous and mesoporous materials, while providing a realistic description of electrostatic fields near surfaces and inside pores of adsorbents and catalysts.

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