Parameterization of ReaxFF

You should have prepared the appropriate geo, trainset.in and params files. For instructions, look at the Parameterization folder.

Change iopt from 0 to 1.

Create params file.

Execute.

fort.79 has the one-line parameterization
Each section delimited by a blank line corresponds to a line in the params file.
The system calculates the total error for the three points in each params line, and then assigns a new value to the parameter based on extrapolation to a value that will reduce the total error. Every four lines in the fort.13 file keeps a running track of the four total errors corresponding to the shen the negative increment, positive incrementm original and extrapolated values are used for that parameter.

fort.83 has the changes to the ffield. Take the last section for your new ffield (if restarting or using for an MD run)
fort.90 has the updated geometry. Copy to geo (if restarting or using for an MD run)
fort.99 compares the latest optimized set ReaxFF data with the reference (typically QM) data.

A strategy to iterate this process is to paste multiple copies of the params to be optimized in the params file rather than iterating one set at a time.

Might not need the bond distance and angle information if already in good shape. Concentrate on charges and energies? What goes into the trainset.in file will obviously weight what is important so pay heed to what is put in.

Don't forget to change iopt back to 0 if no longer optimizing parameters.