We studied silica dimerization reactions in the gas and aqueous phase by density functional theory (DFT) and reactive force fields based on two parameterizations of ReaxFF. For each method (both ReaxFF force fields and DFT), we performed constrained geometry optimizations, which were subsequently evaluated in single point energy calculations using the other two methods. Standard fitting procedures typically compare the force field energies and geometries with those from quantum mechanical data after a geometry optimization. The initial configurations for the force field optimization are usually the minimum energy structures of the ab initio database. Hence, the ab initio method dictates which structures are being examined and force field parameters are being adjusted in order to minimize the differences with the ab initio data. As a result, this approach will not exclude the possibility that the force field predicts stable geometries or low transition states which are realistically very high in energy and, therefore, never considered by the ab initio method. Our analysis reveals the existence of such unphysical geometries even at unreactive conditions where the distance between the reactants is large. To test the effect of these discrepancies, we launched molecular dynamics simulations using DFT and ReaxFF and observed spurious reactions for both ReaxFF force fields. Our results suggest that the standard procedures for parameter fitting need to be improved by a mutual comparative method.
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14 November 2015
Research Article|
November 12 2015
A test on reactive force fields for the study of silica dimerization reactions
Mahmoud Moqadam;
Mahmoud Moqadam
Department of Chemistry,
Norwegian University of Science and Technology (NTNU)
, Høgskoleringen 5, Realfagbygget D3-117, 7491 Trondheim, Norway
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Enrico Riccardi;
Enrico Riccardi
Department of Chemistry,
Norwegian University of Science and Technology (NTNU)
, Høgskoleringen 5, Realfagbygget D3-117, 7491 Trondheim, Norway
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Thuat T. Trinh;
Thuat T. Trinh
Department of Chemistry,
Norwegian University of Science and Technology (NTNU)
, Høgskoleringen 5, Realfagbygget D3-117, 7491 Trondheim, Norway
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Per-Olof Åstrand
;
Per-Olof Åstrand
Department of Chemistry,
Norwegian University of Science and Technology (NTNU)
, Høgskoleringen 5, Realfagbygget D3-117, 7491 Trondheim, Norway
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Titus S. van Erp
Titus S. van Erp
a)
Department of Chemistry,
Norwegian University of Science and Technology (NTNU)
, Høgskoleringen 5, Realfagbygget D3-117, 7491 Trondheim, Norway
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a)
Electronic mail: titus.van.erp@ntnu.no.
J. Chem. Phys. 143, 184113 (2015)
Article history
Received:
August 03 2015
Accepted:
October 24 2015
Citation
Mahmoud Moqadam, Enrico Riccardi, Thuat T. Trinh, Per-Olof Åstrand, Titus S. van Erp; A test on reactive force fields for the study of silica dimerization reactions. J. Chem. Phys. 14 November 2015; 143 (18): 184113. https://doi.org/10.1063/1.4935179
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