Input files¶

In order to optimize a ReaxFF forcefield, the files listed below must be present in the directory where the reaxff program is executed.

• iopt – file containing a single text line with 4 on it, written in the (i3) format. This will instruct reaxff to perform a Monte-Carlo force-field optimization.
• ffield – the initial force-field file.
• ffield_min – minimum values for each force-field value (this file has the same format as ffield).
• ffield_max – maximum values for each force-field value (this file has the same format as ffield).
• ffield_bool – contains 1.0 or 0.0 as a flag whether the corresponding value is to be optimized or not (this file has the same format as ffield).
• trainset.in – file with test values, the same as in the original reaxff force-field optimization, see page 27 of the ReaxFF User Manual.
• geo – file with test geometries in the BGF format, the same as in the original reaxff force-field optimization. Geometries of different molecules in this file must be concatenated.
• control – in addition to general ReaxFF control parameters it also contains the MCFFOptimizer-related ones explained below.

The mcffopt_water example in the examples/reaxff directory demonstrates the use of the MCFFOptimizer. Note however that this example is not physically meaningful. For example, many atomic force-field parameters are allowed to vary in a very broad range, which is the same for all elements. In practice, you will want to set the range for each element separately.