Hi Zhan,
On Mon, Jul 7, 2014 at 3:40 AM, ZHAN Fei <zhan...@ihep.ac.cn> wrote: > Hi Matti, > Thanks for your attention and patience. > The back fourier transform of the specific peak (use window)of Chi(R) > gives the amplitude,donated by amp_bft。As in previous mails,I ask whether > the compare the amp_bft and the amplitude of specific Z number element can > determine the Z. > Sorry, I'm not sure I understand this. I didn't understand the figure you attached in your earlier mail. Generally speaking, I find back-transformed data to be not very useful -- making any sense of these requires very well isolated shells of atoms. The amplitude of the back-transformed chi(k) (is that what you mean by amp_bft??) has many contributions, and is not simply f(k). It will have Z dependence, but it will have other dependencies too. > And thanks for telling me the useful trick using the total phase shift of > the specific element. > > > The discrepancy between R and Rphcor is below,the Zn and Br is close to > Se(the best fit)'s 0.013, > Yes, Ge actually gives the closest match, and Se the second closest match, and I left Ga out of the test. I would probably say that anything closer that 0.015 Ang (and, really, maybe 0.02 Ang) is pretty darn close. So the phase-correction approach appears to be (in this case) not as sensitive to Z as the reduced chi-square, but does provides a check on self-consistency. The fits with Zn and Rb are noticeably worse than the fit with Se... hence Z +/- 3 or perhaps 5 seems like a reasonable rule of thumb, and sometimes one might be able to do better. > should the enot also be important criterion in this trick?and dose the > plus or minus of enot indicate the lighter or higher element relative to > the specific coordination shell? > Well, an E0 shift > 10 eV probably indicating that something is off .... but that could be just the selection of E0 for the experimental data. I wouldn't put much meaning of the absolute value of E0 though for any single fit. "a bond valence sum can be an independent check on the consistency of N, > R, and valence",can your give the ref. paper of this method? Thanks > > http://en.wikipedia.org/wiki/Bond_valence_method The idea is that N, R, and valence are not independent. --Matt
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