See note here: https://doi.org/10.1021/acs.jctc.1c00975
“The ReaxFF forcefields used for this study are provided in the Supporting Information and based on the forcefield used in Achtyl et al.47 In general, the QEq water forcefield is trained for density and diffusion. For the ACKS2 forcefield, two ACKS2-specific parameters were tuned against the same training data via a relatively simple single-parameter-at-a-time search while keeping the same QEq water forcefield parameters for the rest. A more rigorous ACKS2 forcefield would require a full reparameterization against the training data that includes the atomic parameters, bonded parameters, angle parameters, etc. As such, the fitting of the ACKS2 parameters will cause deviations from the QEq water behavior, where the full QEq parameterization was optimized against the DFT training data.”
Only you can determine what is needed for your research. We don’t have ACKS2 files in the LAMMPS repo other than water, but you could reach out to Adri van Duin and see if he has others.