[Ifeffit] Larch 0.9.37 now available

Matt Newville newville at cars.uchicago.edu
Mon Mar 26 21:07:12 CDT 2018

Hi Folks,

I'm happy to announce the release of Larch 0.9.37.  It's been a while since
I announced updates to Larch, and there has been steady progress on a
number of areas over the past year.  While much of the effort has been
centered on X-ray fluorescence imaging and diffraction mapping work done at
X-ray microprobes especially at GSECARS, there has also been been some work
on XAFS and XANES.

Larch now includes both Feff6l and Feff8l (that is, Feff85 for EXAFS-only
calculations), with routines for running these from within Larch scripts or
from Python.

I want to draw your attention in particular to the program with the rather
boring name "XAS Viewer" (formerly XYFit) that is included with Larch and
may be of interest to several Ifeffit users.  XAS Viewer is currently
focussed on doing pre-edge peak fitting, but we do intend to add more XANES
and EXAFS visualization and analysis tools.  Feedback and suggestions of
any kind would be helpful and greatly appreciated.

Currently, XAS Viewer can read data from plain ASCII files or from recent
"new-style" Athena Project files. Like Athena, it can merge groups and plot
one or more XAFS spectra in various stages of the XAFS normalization
process.  XAS Viewer can also save data to Athena Project file, or save
multiple data sets to CSV files.

While XAS Viewer does basic XANES processing (normalization, etc) and
visualization similar to Athena, its main emphasis is on fitting of
pre-edge peaks.  A dedicated panel helps the user first fit a baseline
curve, then adds peaks (Gaussian, Lorentzian, Voigts, etc) and fits the
entire model to the pre-edge region.  Bounds and constraints can be placed
on any of the parameters for the peaks, and full fit reports including
uncertainties are generated.  Fit models can be saved to a file and
re-loaded.  These saved models can be used from Python code. We will soon
be generating fitting scripts for batch processing, but this is still work
in progress.  Some screenshots, and a bit more information are at


Again, feedback or suggestions on this or any other aspects of Larch are
most welcome.

Larch can be installed with installers for Windows, Mac OSX, Linux.  At the
moment, these installers all assume 64-bit operating systems.  If anyone
needs to use Larch with 32-bit Windows please let me know, and I will try
to build an installer for that platform.  Larch can also be installed as a
"conda package" for Anaconda Python, as with

    conda install -c GSECARS xraylarch

Currently both Python 2.7 or 3.6 are supported.

Finally, Larch can also be used as the "backend" for Athena/Artemis, and I
strongly encourage all Athena/Artemis users to install Larch so that it can
be used in place of the old and unsupported ifeffit library.

--Matt Newville
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