Re: [Ifeffit] synthesis of EXAFS via larch

That's Fantastic. Thanks for swift reply, Matt. Best regards, Kate On 20 March 2018 at 18:35, Matt Newville wrote:

Hi Katy,

On Tue, Mar 20, 2018 at 11:34 AM, Katy Smith wrote:

...

I seem to be able to make some progress in using Larch, thanks to the developers. I wish to produce a plot in R rather than k, what would be the equivalent commands to ff2chi, path.k etc as per the /examples/feffit/doc_feffdat3.lar?

The sum with `ff2chi` only sums in k-space. But the output is ready to do a Fourier transform with `xftf` (short for "XAFS Fourier Transform Forward"). So, building on doc_feffdat3.lar, you could do

# sum of paths (assumed to be defined already), writing chi(k) to "mysum": ff2chi([path1, path2, path3, path4, path5], group=mysum)

# now do an XAFS Fourier transform on that group to go from k to R space: xftf(mysum, kweight=2, kmin=3, kmax=15, window='kaiser', dk=4)

# plot of |chir(R)| for this sum plot(mysum.r, mysum.chir_mag, label='sum of paths', xlabel=r'$R \rm\,(\AA)$',ylabel=r'$|\chi(R)| \rm\,(\AA^{-3})$')

We're working to release the next version of Larch very soon, which includes common xafs plotting commands so that the last line there could be written as "plot_chir(mysum, label='sum of paths')".

--Matt

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