Stephens peakshape and lattice parameter distribution

ben-smith

I have been using stephens peakshape (specifically stephens hexagonal) to refine anisotropic peak broadening in my data. It is my understanding from reading the original paper (P.W. Stephens, J. Appl. Cryst. (1999) 32, 281-9)) that the refined parameters, s400, s004, s220 describe a gaussian distribution of lattice parameters throughout the sample. What units does TOPAS report S004 etc in?

Is it possible to go from these to the lattice parameter distributions, e.g can you go from the refined S004 parameter to a distribution or uncertainty in the c lattice parameters?

Thanks for any help!