Thanks, Bruce.
Does the math expression in IFEFFIT include the term -4k*sigma2*(1/labmda
+1/R) in the phase? If yes, the 1st cumulant is sigma1= R+dR. If no, sigma1=
R+dR+2*sigma2*(1/labmda +1/R). It this correct?
Yuan
On 4/1/11 2:18 PM, "Bruce Ravel"
On Friday, April 01, 2011 05:03:17 pm Ping, Yuan wrote:
Dear IFEFFIT experts:
Is it possible to add a k^3 term in the phase for fitting to take into account anharmonic effect? The fitted coefficient will be proportional to the 3rd cumulant of Debye-Waller factor. I work with high-temperature high-pressure systems where anharmonic effect is not negligible.
Thanks. Yuan Ping
Hi Yuan,
Here is the relevant page from the Ifeffit reference manual:
http://cars9.uchicago.edu/~ifeffit/refman/node51.html
You want to use the "3rd" path parameter, which adds a term proportional to C3*k^3 to the sine function in the exafs equation.
See the attached figure for the place in Artemis where this parameter is introduced.
HTH, B