Bond breaking in epoxy systems: A combined QM/MM approach

A novel method to combine quantum mechanics (QM) and molecular mechanics has been developed to accurately and efficiently account for covalent bond breaking in polymer systems under high strain without the use of predetermined break locations. Use of this method will provide a better fundamental und...

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Bibliographic Details
Published in:The Journal of chemical physics 2016-06, Vol.144 (24), p.244904-244904
Main Authors: Barr, Stephen A., Kedziora, Gary S., Ecker, Allison M., Moller, James C., Berry, Rajiv J., Breitzman, Tim D.
Format: Article
Language:English
Subjects:
BOND LENGTHS
CHEMICAL BONDS
COMPUTER CALCULATIONS
Computer simulation
COMPUTERIZED SIMULATION
Covalent bonds
Energy conservation
Hybrid systems
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
Mathematical analysis
Optimization
Organic chemistry
Physics
QUANTUM MECHANICS
STRAINS
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Summary:A novel method to combine quantum mechanics (QM) and molecular mechanics has been developed to accurately and efficiently account for covalent bond breaking in polymer systems under high strain without the use of predetermined break locations. Use of this method will provide a better fundamental understanding of the mechano-chemical origins of fracture in thermosets. Since classical force fields cannot accurately account for bond breaking, and QM is too demanding to simulate large systems, a hybrid approach is required. In the method presented here, strain is applied to the system using a classical force field, and all bond lengths are monitored. When a bond is stretched past a threshold value, a zone surrounding the bond is used in a QM energy minimization to determine which, if any, bonds break. The QM results are then used to reconstitute the system to continue the classical simulation at progressively larger strain until another QM calculation is triggered. In this way, a QM calculation is only computed when and where needed, allowing for efficient simulations. A robust QM method for energy minimization has been determined, as well as appropriate values for the QM zone size and the threshold bond length. Compute times do not differ dramatically from classical molecular mechanical simulations.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.4954507