[Ifeffit] Dynamic XAFS Simulations?

Robert Gordon ragordon at alumni.sfu.ca
Wed Jan 23 16:53:04 CST 2019


Welcome to XAFS and all the excitement, thrills and adventure that implies!

First, since you are new to the subject, I would strongly recommend you 
take a course
on XAFS. Many synchrotron facilities offer such - e.g. The APS/IIT 
Summer school was held
last July; the SSRL course was last August, and NSLS2 had theirs in 
November. Any schools
being held this year will likely also be announced on this iFeffit 
mailing list.

Some other resources for learning the basics can be found here:
Matt's introduction is a good place to start.

For "dynamic XAFS" searches, you should consider "pump probe xafs" or 
"time-resolved xafs"
as search terms. Searching for pump probe xafs for me easily yielded 
this article

As for simulation of XAFS, one program is FEFF, developed by the Rehr 
Group at the University of Washington
FEFF9 (8, 7) requires a license and modest fee for academic use, and is 
widely used for simulating both the
near edge and extended fine structure. Bruce Ravel's Demeter suite of 
programs for XAFS processing and analysis
includes an earlier version (FEFF6). Demeter is free - mostly a labour 
of love by Bruce, and he likes beer and maple syrup if you happen to run 
into him at a conference.

FDMNES (Yves Joly group, Institut Neel) is another program for 
simulating the near-edge. I find it works
quite well. It allows for tweaking of the starting electronic 
configuration as well (with cautionary notes) that
might be useful for simulating excited systems (I haven't checked 
literature to see if anyone has done so).

An additional program of note for fitting and simulation is GNXAS 
(DiCicco group, U. Camerino) but I haven't
used it myself.

I am probably overlooking others, but these should get you going. I 
strongly recommend you take a course
on the basics before plunging into any of these.


On 2019-01-23 1:26 p.m., Hunter Allison wrote:
> Hi,
>       I'm a graduate student at the University of California, Irvine. 
> Firstly, thank you for all the copious resources. It is a treasure 
> trove of information and a beacon of light for someone just starting out.
>      Let's begin with some brief background. In my research group, we 
> intend to perform pump-probe spectroscopy with attosecond x-ray 
> probes. The Professor says that we can use XAFS to study how the 
> electrons move on these very short timescales. While the system is 
> being setup and other experiments are being conducted, my Professor 
> wants me to figure out how to do simulations of XAFS. This is a bit of 
> a daunting order, since I've never simulated anything before and only 
> have basic programming knowledge. The only direction I have is, "Try 
> Google.".
>      So, today, I've been "trying Google" and found my way to here. 
> Since, I don't really know what I'm doing, I thought I try asking and 
> finding out if anyone else does this sort of thing:
> How/where does one do simulations of dynamic XAFS? Where would I get 
> started?
> (Please forgive me if this question has been answered somewhere else 
> or if it seems profoundly dumb or too broad. I'm really just looking 
> for some more direction. Perhaps, it could be that nobody does this 
> and, in that case, I need to figure out how to model this myself. Wow! 
> That thought seems daunting.)
>      For example, let's say I want to find out how the x-ray 
> adsorption of a carbon foil like Graphene would change on attosecond 
> time scales as it's heated by a femtosecond laser and electrons move. 
> Is there a program or code out there that people use to model this 
> sort of thing?
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