Message 86: error - calculated 3-body potential index too large

DL_POLY_2 has a permitted maximum for the calculated index for any three body potential in the system (i.e. as defined in the FIELD file). If there are $m$ distinct types of atom in the system, the index can possibly range from $1$ to $(m^{2}*(m-1))/2$. If the internally calculated index exceeds this number, this error report results.

Action:
Standard user response. Fix the parameter mxtbp.