[lammps-users] bond_fene equilibrium_distance

Hi, all. Just a minor point. In bond_fene.cpp, the “equilibrium_distance” function returns .97*sigma. Actually, the minimum of the FENE potential for the standard parameters (k = 30, R_0 = 1.5, epsilon = 1.0, sigma = 1.0) is at .960897. So, while .97 may be the actual equilib. distance for the standard temperature T = 1.0 epsilon/k_B, this result is not general, and besides depends on the parameters k and R_0.


I think it's only used when bonds are SHAKEd. I doubt
anyone SHAKEs FENE bonds, so it's really juts a placeholder.


Rob - do you have the formula for this handy? I presume its from
setting the derivative of the potential to 0. If so, I'll make
it more general, though I'll still need to assume that T = 1.0
or something reasonable.