Scott said:
It is my secret, completely untested belief (which I am now revealing to everyone on this mailing list!), that some of the cases of "successful" fits using multiple E0's are masking problems caused by not considering a third cumulant.
Hmm, really??? I'm not sure of that. Even disregarding the different k-dependences of E0 and C3, I'm not sure how using different E0's for different paths (especially with the notion that they are to be applied to different coordination species) could mask a third cumulant for a particular path. Do you have an example? As discussed earlier, using different E0's for different shells does have some physical interpretation: that the single, flat energy origin from the muffin tin approximation is incomplete. That's about as physical as the first E0 and S02. My guess is that a second E0 is about as likely to be needed as non-zero C3 unless you have purposely disordered (that is, hot) samples. It's certainly easy enough to add fudge factors to a fit. The hope is that the model has some physical meaning or that a reviewer would catch abuses! --Matt