ReaxFF is a force field

Force field (chemistry)

In the context of molecular modeling, a force field refers to the form and parameters of mathematical functions used to describe the potential energy of a system of particles . Force field functions and parameter sets are derived from both experimental work and high-level quantum mechanical...

 developed by Adri van Duin, William A. Goddard, III

William A. Goddard, III

William Andrew Goddard III is the Charles and Mary Ferkel Professor of Chemistry and Applied Physics, and Director, Materials and Process Simulation Center at the California Institute of Technology. He obtained his B.S. from the University of California, Los Angeles, in 1960 and his Ph.D...

 and co-
workers at the California Institute of Technology

California Institute of Technology

The California Institute of Technology is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering...

 for use e.g. in molecular dynamics

Molecular dynamics

Molecular dynamics is a computer simulation of physical movements of atoms and molecules. The atoms and molecules are allowed to interact for a period of time, giving a view of the motion of the atoms...

 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

Bond order potential

Bond order potential is a class of empirical potentials used, e.g., in molecular dynamics and molecular statics simulations. Examples include the Tersoff potential, the Brenner potential, the Finnis-Sinclair potentials...

, which allows for continuous bond formation/breaking. ReaxFF aims to be as general as possible and has been parameterized and tested
for hydrocarbon reactions, transition-metal-catalyzed nanotube formation, and high-
energy materials.