Hi Harry, 




On Fri, Aug 19, 2022 at 9:10 AM Andy Zhang <hzhangcat@gmail.com> wrote:
Dear all,

I have a quick question related to EXAFS fitting using Larch. I wonder how to include the third cumulant in the fitting. I tried to add "third" in the "pars" section, but it seems it did not work.

image.png

Thanks a lot for your help!


By itself, that just sets up the parameters to be varied during the fit.  It does not specify how those will be used.

So: did you use the parameter named "third" in any of the Path Parameter definitions?  Something like this

     path1 = feffpath('feff0001.dat',   s02 = 'amp', e0 = 'del_e0',   sigma2='sigma2_eins(300, theta)',  
                               deltar='alpha*reff', 
                               third='third')

should work. 

If not, please post a complete, minimal example showing what you are doing.

--Matt