<div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">There are two fundamental issues:</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">a) How to handle the dynamical diffraction of the swift electrons.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)">b) How to handle the core hole.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:rgb(0,0,0)"><br></div><div class="gmail_default"><font color="#000000" face="verdana, sans-serif">To my knowledge no DFT code handles a) correctly. (Some details are in Chpt 5 of </font>"High-Resolution Transmission Electron Microscopy: and Associated Techniques" Eds Buseck, Cowley and Eyring.) Particularly if you are on a zone axis dynamical diffraction effects (often called channeling, but this is not fully rigorous in my opinion) can be very strong. One way to minimize the effect is to tilt off the zone axis to a pseudo-kinematical condition. Of course, by doing this you lose imaging. You might (very might) be able to reduce the issue by using a larger collection angle making it similar to Precession (e.g. DOI 10.1016/j.ultramic.2012.11.007). I am not sure if people have really explored this enough.<br></div><div class="gmail_default"><br></div><div class="gmail_default">For the core hole, from what I have seen (I am not a full EELS expert) often how much of a core hole one wants is an "adjustable parameter". At least with Slater Transition Theory it should only be 1/2 a hole.</div><div class="gmail_default"><br></div><div class="gmail_default">Not an easy problem, and I am not convinced that it has been fully solved although I would be willing to be proved wrong.</div></div></div><br><div class="gmail_quote"><div dir="ltr">On Mon, Oct 15, 2018 at 6:54 AM yfding <<a href="mailto:yfding0375@foxmail.com">yfding0375@foxmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div><font size="2" style="line-height:22.1px"><span style="font-size:14px">This problem haunts me for nearly a year,</span> and
</font><span style="font-size:small">my questions are still unsolved after consulting a lot of literature and mailing list</span><span style="font-size:small">.
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<div><span style="font-size:small">I tried to get Oxygen K edge of the 3*3*3 SrCrO3 supercell.</span></div>
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<div><font size="2" style="line-height:22.1px">In my calculations, I first converted the SrCrO3 (space group P4/mmm) into a SrCrO3 3*3*3 supercell (space group P1) in CrystalMaker, then transformed the SrCrO3supercell.cif file into
</font><span style="font-size:small">SrCrO3supercell</span><span style="font-size:small">.struct file under the Wien2k case directory, labelled one oxygen atom to make this atom unique, did initialization, and accepted all the queries from nn complaints.
The initialization parameters were as follows:</span></div>
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<div><font style="line-height:22.1px" size="2"> Rmt: Sr:2.40 Cr:1.78 O:1.61
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<div><span style="font-size:small"> potential: GGA of PBE-96</span></div>
<div><font style="line-height:22.1px" size="2"> separation energy: -6.0 Ry</font></div>
<div><font style="line-height:22.1px" size="2"> RKmax: 7.0</font></div>
<div><font style="line-height:22.1px" size="2"> Max L in WF: 10</font></div>
<div><font size="2"> number of k points in the whole BZ: 5*5*5</font></div>
<div><span style="font-size:small"> number of k points in the irreducible wedge of the BZ: 18</span></div>
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<div><font size="2">Then I edited SrCrO3.inc and removed one core electron from the 7th atom, i.e. 1st Oxygen atom 1s state. Next I changed 0.0 to -1.0 in SrCrO3.inm. Then run SCF in parallel (energy convergence 0.0001 Ry).
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<div><font size="2">Then, </font></div>
<div><font size="2">-edited case.innes :</font></div>
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<div><font size="2"> SrCrO3 O K edge</font></div>
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<div> 7 (atom)</div>
<div> 1, 0 (n, l core)</div>
<div> 532 (E-Loss of 1st edge in eV)</div>
<div> 200 (energy of the incident electrons in keV)</div>
<div> -5.0 20.0 0.1 (minimum energy, energy step, maximum energy)</div>
<div> 0.37 0.75 (collection semiangle, convergence semiangle, both in mrad)</div>
<div> 50 1 (NR, NT, defining the integration mesh in the detector plane)</div>
<div> 0.7 (spectrometer broadening in eV)</div>
<div> OUTPUT</div>
<div> 0 (full output)</div>
<div> DETECTOR POSITION</div>
<div> 0.0 0.0 (thetax, thetay)</div>
<div> MODUS</div>
<div> energy (dscs wrt what?)</div>
<div> ORIENTATION SENSITIVE</div>
<div> 0.0 0.0 0.0</div>
<div> SELECTION RULE</div>
<div> n (selection rule)</div>
<div> LSELECTION RULE</div>
<div> d</div>
<div> INITIALIZATION</div>
<div> y y (dos and xdos handling)</div>
<div> y y (handling of rotation matrices)</div>
<div> QGRID</div>
<div> U</div>
<div> END</div>
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<div><font size="2">- x lapw1</font></div>
<div><font size="2">- x lapw2 -qtl </font></div>
<div><font size="2">- x qtl -telnes</font></div>
<div><font size="2">- x telnes3</font></div>
<div><font size="2">- x broadening</font></div>
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<div>As it is supercell, I calculated every peak of unequivalent O K edge and summed them. I'm not sure all the steps I have done are right. The result is different from the TEM EELS experiment (The O K edge EELS spectra were studied on an JEOL
ARM200F Cs-corrected TEM with a FEG and a Gatan parallel electron-energy-loss spectroscope). The relative strength and position of the peaks are completely inconsistent.
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<div>It's not just this example, but I've had the same problem with all the other materials. I thought about all the possible reasons, and looked up lots of literature and mailing lists, but I couldn't get the calculation results closer to the
experiment. I want to know how to obtain ELNES simulation results consistent with experiments ?</div>
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<div><span style="font-size:14px">Any comment(s) would be highly appreciated.
</span>Thanks in advance!</div>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><span style="font-size:12.8px">Professor Laurence Marks</span><br></div><div dir="ltr"><span style="font-size:12.8px">"Research is to see what everybody else has seen, and to think what nobody else has thought", </span><span style="font-size:12.8px">Albert Szent-Gyorgi</span><br><a href="http://www.numis.northwestern.edu" target="_blank">www.numis.northwestern.edu</a> ; <span style="font-size:12.8px">Corrosion in 4D: </span><a href="http://MURI4D.numis.northwestern.edu" style="font-size:12.8px" target="_blank">MURI4D.numis.northwestern.edu</a><div><span style="font-size:12.8px">Partner of the CFW 100% program for gender equity, </span><a href="http://www.cfw.org/100-percent" style="font-size:12.8px" target="_blank">www.cfw.org/100-percent</a></div><div>Co-Editor, Acta Cryst A</div></div></div></div></div></div></div></div></div></div></div>