In addition to what Axel says, 0.25 fs seems like a large time step for reax.
I would recommend trying a few runs with shorter time steps like 0.1 fs or 0.05 fs.
Because of it’s piecewise potential energy form, the force gradient in reax can have large
spikes, depending on the parametrization and system type, which leads to need smaller
time steps.
Ben Jensen
Michigan Technological University