Hi Matthew, XNCD is due to dipole-quadrupole interference terms. See for example, Ankudinov, Phys. Rev. B 62, 2437–2445 (2000) Cheers, Josh On Wed, Sep 11, 2013 at 12:18 PM, wrote:

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Today's Topics:

1. X-ray natural circular dichroism by FEFF? (Joshua Kas) 2. Re: X-ray natural circular dichroism by FEFF? (Matthew Marcus)

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Message: 1 Date: Wed, 11 Sep 2013 10:59:37 -0700 From: Joshua Kas To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] X-ray natural circular dichroism by FEFF? Message-ID: Content-Type: text/plain; charset="iso-8859-1"

Hi Matthew, Sorry it took a while to answer your questions. No one has used the XNCD features of FEFF for quite some time, and the example files that were lying around did not run correctly. However, I have now reproduced the output from one for the LiIO3 example. Please see the input below. The main things that are essential are: 1. The setting MULTIPOLE 2 which turns on quadrupole effects. 2. The XNCD card. 3. The ELLIPTICITY card to tell the program the direction of x-ray propagation, i.e., ELLIPTICITY elipticity kx ky kz for example, circular polarization in the z direction is specified by ELLIPTICITY 1 0 0 1 If you don't specify the ELLIPTICITY, and the XNCD card is specified, the program will assume circularly polarized light traveling in the z direction.

I am also attaching the results that I get from FEFF9. The xncd signal is in column 6.

Cheers, Josh Kas

* Example feff input file for XNCD of LiIO3 * This feff.inp file generated by ATOMS, version 2.46c * ATOMS written by Bruce Ravel and copyright of The Univ. of Washington, 1994

* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * total mu = 112.7 cm^-1, delta mu = 92.0 cm^-1 * specific gravity = 4.488, cluster contains 547 atoms. * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * mcmaster corrections: 0.00014 ang^2 and 0.403E-07 ang^4 * self-abs. corrections: amplitude factor = 4.652 * 0.00011 ang^2 and 0.252E-07 ang^4 * i0 corrections: 0.00006 ang^2 and 0.269E-07 ang^4 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * * sum of corrections: 0.00031 ang^2 and 0.923E-07 ang^4 * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *

TITLE LiIO3

HOLE 4 1.0 I L3 edge, second number is S0^2 SCF 4.0

* pot ph fms paths genfmt ff2chi CONTROL 1 1 1 1 1 1

XANES 5.5 0.05 0.5 * absorption with averaging over left and right circular polarizations *POLARIZATION 1 0 0 MULTIPOLE 2 ELLIPTICITY 1 0 0 1

* XNCD calculations; comment out for above average absorption XNCD

EXCHANGE 0 1 0.0 2 RPATH 0.1

* 41-atom cluster FMS 4.9

POTENTIALS * ipot z label l_scmt l_fms 0 53 I 3 3 0.01 1 8 O 2 2 3.00 2 3 Li 2 2 1.00 3 53 I 3 3 0.99

ATOMS 0.00000 0.00000 0.00000 0 I 0.00000 -0.40916 -1.44312 -0.88847 1 O 1.74338 -1.13161 1.09916 -0.88847 1 O 1.81055 1.54125 0.34316 -0.88847 1 O 1.81179 0.04130 2.19081 1.85203 1 O 2.86903 -2.03253 -0.99669 1.85203 1 O 2.92482 1.99171 -1.19491 1.85203 1 O 2.97064 -1.58207 -2.53476 0.41875 2 Li 3.01717 -1.58207 2.63724 0.41875 2 Li 3.10376 3.16461 -0.10326 0.41875 2 Li 3.19387 0.04130 -2.98119 1.85203 1 O 3.50988 2.71415 1.43481 1.85203 1 O 3.58543 -2.75498 1.54559 1.85203 1 O 3.66180 -1.58207 -2.53476 -2.32175 2 Li 3.78398 -1.58207 2.63724 -2.32175 2 Li 3.85337 -0.40916 3.72888 -0.88847 1 O 3.85504 3.16461 -0.10326 -2.32175 2 Li 3.92632 -3.20544 -2.08834 -0.88847 1 O 3.92751 1.58207 2.53425 -2.74050 3 I 4.05410 1.58207 2.53425 2.74050 3 I 4.05410 3.61508 -1.64134 -0.88847 1 O 4.06843 1.58207 -2.63775 2.74050 3 I 4.11959 1.58207 -2.63775 -2.74050 3 I 4.11959 -3.16461 0.10275 2.74050 3 I 4.18756 -3.16461 0.10275 -2.74050 3 I 4.18756 0.04130 2.19081 -3.62897 1 O 4.23919 -2.03253 -0.99669 -3.62897 1 O 4.27715 1.99171 -1.19491 -3.62897 1 O 4.30861 -1.13161 -4.07284 -0.88847 1 O 4.31948 -1.58207 -2.53476 3.15925 2 Li 4.34843 -1.58207 2.63724 3.15925 2 Li 4.40895 3.16461 -0.10326 3.15925 2 Li 4.47284 -3.20544 3.08366 -0.88847 1 O 4.53577 4.33752 0.98838 -0.88847 1 O 4.53656 0.04130 -2.98119 -3.62897 1 O 4.69666 2.71415 1.43481 -3.62897 1 O 4.75339 -2.75498 1.54559 -3.62897 1 O 4.81125 1.99171 3.97709 1.85203 1 O 4.81811 -0.40916 -1.44312 4.59253 1 O 4.83129 -1.13161 1.09916 4.59253 1 O 4.85593 1.54125 0.34316 4.59253 1 O 4.85639 -2.75498 -3.62641 1.85203 1 O 4.91638 2.71415 -3.73719 1.85203 1 O 4.97627 -2.03253 4.17531 1.85203 1 O 4.99944 -4.70539 -0.24069 1.85203 1 O 5.06247 3.61508 3.53066 -0.88847 1 O 5.13066 1.54125 -4.82884 -0.88847 1 O 5.14611 4.78798 -0.54969 1.85203 1 O 5.16304 0.00000 -5.17200 0.00000 3 I 5.17200 0.00000 5.17200 0.00000 3 I 5.17200 -4.74669 -2.43150 0.00000 3 I 5.33322 4.74669 2.43150 0.00000 3 I 5.33322 -5.15585 1.29738 -0.88847 1 O 5.39030 0.00000 0.00000 5.48100 3 I 5.48100 0.00000 0.00000 -5.48100 3 I 5.48100 4.74669 -2.74050 0.00000 3 I 5.48100 -4.74669 2.74050 0.00000 3 I 5.48100 1.99171 3.97709 -3.62897 1 O 5.74052 1.54125 5.51516 -0.88847 1 O 5.79499 -2.75498 -3.62641 -3.62897 1 O 5.82324 2.71415 -3.73719 -3.62897 1 O 5.87390 -1.58207 -2.53476 -5.06225 2 Li 5.87830 -2.03253 4.17531 -3.62897 1 O 5.89354 -1.58207 2.63724 -5.06225 2 Li 5.92320 -0.40916 3.72888 4.59253 1 O 5.92987 -4.70539 -0.24069 -3.62897 1 O 5.94710 3.16461 -0.10326 -5.06225 2 Li 5.97092 -3.20544 -2.08834 4.59253 1 O 5.97723 3.16461 5.06874 0.41875 2 Li 5.99018 END

On Tue, Sep 10, 2013 at 10:00 AM, wrote:

...

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Today's Topics:

1. X-ray natural circular dichroism by FEFF? (Matthew Marcus)

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Message: 1 Date: Tue, 10 Sep 2013 09:28:44 -0700 From: Matthew Marcus To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] X-ray natural circular dichroism by FEFF? Message-ID: <522F48BC.8090402@lbl.gov> Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Can FEFF calculate X-ray natural circular dichroism, which is the XCD that comes from structural chirality and not magnetism? I suppose I could simply try it, putting in coordinates for some simple molecule, but I'd like to know if any results would be meaningful. mam

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