ReaxFF (for “reactive force field”) is a bond order-based
force field developed by Adri van Duin,
William A. Goddard, III, and co-workers at the
California Institute of Technology
The California Institute of Technology (branded as Caltech or CIT)The university itself only spells its short form as "Caltech"; the institution considers other spellings such a"Cal Tech" and "CalTech" incorrect. The institute is also occasional ...
. One of its applications is
molecular dynamics simulations. Whereas traditional force fields are unable to model chemical reactions because
of the requirement of breaking and forming bonds (a force field's functional form depends on having all bonds defined
explicitly), ReaxFF eschews explicit bonds in favor of
bond orders, which allows for continuous bond formation/breaking. ReaxFF aims to be as general as possible and has been parameterized and tested for hydrocarbon reactions, alkoxysilane gelation, transition-metal-catalyzed nanotube formation, and many advanced material applications such as Li ion batteries, TiO
2, polymers, and high-energy materials.
To be able to deal with bond breaking and formation whilst having only 1 single atom type for each element, ReaxFF is a fairly complex force field with many parameters. Therefore an extensive training set is necessary covering the relevant chemical phase space, including bond and angle stretches, activation and reaction energies, equation of state, surface energies, and much more. Usually, but not necessarily, the training data is generated with electronic structure methods. In practice, often
DFT calculations are used as a pragmatic approach, especially since more accurate functionals are available.
For the parameterization of such a complex force field,
global optimization techniques offer the best chance to get a parameter set that most closely describes the training data.
References
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*{{Cite journal , doi = 10.1021/jp504138r, title = Parallel Optimization of a Reactive Force Field for Polycondensation of Alkoxysilanes, journal = The Journal of Physical Chemistry B, volume = 118, issue = 37, pages = 10966–10978, year = 2014, last1 = Deetz , first1 = J. D. , last2 = Faller , first2 = R. , pmid = 25153668
External links
Adri van Duin's WebsiteReaxFF in the Amsterdam Modeling SuiteReaxFF in PuReMD (Purdue Reactive MD) suite
Force fields