Hi,
While looking at the file pair_sw.cpp in the source directory, I noticed that in the two-body part of the Stillinger-Weber force, there is a term of order “q+1” (q is one of the parameters) which corresponds to the term of order “q” in the two-body part of the energy. In the case of q equals zero, (as for the silicon set of parameters), the derivative of the “q” order term should be zero, but instead of that, the resultant force includes a term proportional to (sigma/r) because the differentiation is done before setting q=0. Should I ajust the force calculation if I set q=0 to eliminate that term ? Thank you for your advise.
Paule