The Tersoff/ZBL potential says that the Tersoff potential used is the one from 1988 (this is found on doc page). However, the 1988 paper is parameterized only for silicon unless I am mistaken. Tersoff published a paper in 1989 for Si, C.
Is this what was meant? I am confused on how the Tersoff potential from 1988 is used when the paper did not provide data for C.