Improved Description of a Coordinate Bond in the ReaxFF Reactive Force Field

To improve the description of a coordinate bond of the reactive force field (ReaxFF), we have developed ReaxFF_coord by explicitly incorporating the coordinate bond contribution, E_coord, into the original ReaxFF ( Chenoweth et al. J. Phys. Chem. A 2008 , 112 , 1040 - 1053 ), in which the auxiliary functions are newly suggested to describe the plug-in behavior of lone-pair electrons from a donor atom to a vacant orbital of an acceptor atom. To validate the developed ReaxFF_coord, we tested it in various systems, including a representative coordinate bond-containing molecule, namely, carbon monoxide or ammonia borane. Although the fitting abilities of the ReaxFF_coord and original ReaxFF are similar, their molecular dynamics (MD) simulations are significantly different, where MD simulations employing ReaxFF_coord provide more realistic dynamic behaviors of atoms. It is expected that the ReaxFF_coord will significantly help ReaxFF to successfully extend its applicability to the material and biological systems, including coordinate bonds in organometallic systems.