ReaxFF is a program for modeling chemical reactions with atomistic potentials based on the reactive force field approach developed by van Duin and coworkers. SCM has implemented and parallelized ReaxFF and significantly optimized the original code, removing memory bottlenecks. Systems consisting of a 3D box of multiple molecules totaling hundreds of thousands of atoms can now be modeled on a modern desktop computer. Parameters are included for many elements not included in traditional force fields, such as a number of transition metals. ReaxFF has been used over the past decade in various studies of inhomogeneous reactive systems, including solvent environments, interfaces, and molecules on metal and metal oxide surfaces.