Re: [Ifeffit] Problem reproducing spectrum for Ti complex (Josh Kas)

Hi Janine, I think that distortions could play a role here. When I shift the central Ti atom by 0.1 angstroms in plane (perpendicular to the Cl bonds) to break the planar symmetry, I get a clear double pre-edge peak. 0.1 angstroms may be a bit large but 0.05 is certainly not, since 0.003 angstroms**2 is a very reasonable value for sigma**2. You could also estimate the distortion if you have more information about the debye waller factors, or even better, you could perform a molecular dynamics simulation and do a configurational average of the XANES spectra from snapshots. Below is the feff.inp file that I used. You might want to play with shifting the Ti atom in different directions too. Cheers, Josh Kas TITLE TiPcCl2 molecule Geom1acc CONTROL 1 1 1 1 1 1 PRINT 5 0 0 0 0 0 FMS 9.0 1 *1 appropriate for molecules (wiki) MULTIPOLE 2 *Dipole and quadrupole EXCHANGE 0 0 0 0 *Dirac Hara, -1eV Fermi level shift, -3 broadening SCF 8.0 1 *includes second coordination shell XANES 6.0 0.03 0.001 AFOLP 1.2 CRITERION 0 0 RPATH 0.1 SIG2 0.005 * emin emax eimag * LDOS -20 20 0.2 POTENTIALS *absorbing atom is the Ti *ipot z tag 0 22 Ti 1 6 C 2 7 N 3 1 H 4 17 Cl ATOMS 0 0.1 0 0 0 -0.00040276 -2.1184 -0.28392 2 2.13734 -2.11835 0.00044201 -0.284329 2 2.13734 0.00049691 2.11839 -0.284036 2 2.13734 2.11844 -0.00045764 -0.283627 2 2.13734 -0.00040584 6.782e-05 2.45003 4 2.45003 0.00040523 -6.766e-05 -2.45005 4 2.45005 -1.14859 2.9207 -0.359915 1 3.159 -1.14983 -2.92023 -0.359755 1 3.159 -2.92016 1.14988 -0.36016 1 3.159 -2.92065 -1.14866 -0.360097 1 3.159 1.14871 -2.92072 -0.359374 1 3.159 1.14995 2.92021 -0.359534 1 3.159 2.92028 -1.1499 -0.359129 1 3.159 2.92077 1.14864 -0.359192 1 3.159 -2.49915 2.50027 -0.371632 2 3.5546 -2.50021 -2.49922 -0.371494 2 3.5546 2.49928 -2.50029 -0.370665 2 3.5546 2.50034 2.4992 -0.370803 2 3.5546 -0.692606 4.24003 -0.468777 1 4.32173 -0.694406 -4.23976 -0.468544 1 4.32173 -4.23967 0.694471 -0.469267 1 4.32173 -4.23997 -0.692696 -0.469229 1 4.32173 0.692761 -4.24006 -0.468314 1 4.32173 0.694562 4.23974 -0.468547 1 4.32173 4.23983 -0.694497 -0.467823 1 4.32173 4.24012 0.69267 -0.467862 1 4.32173 -1.42292 5.42169 -0.582346 1 5.63547 -1.42522 -5.42112 -0.582048 1 5.63547 -5.42101 1.4253 -0.582898 1 5.63547 -5.42161 -1.42303 -0.58282 1 5.63547 1.42311 -5.42172 -0.581576 1 5.63547 1.42541 5.42109 -0.581873 1 5.63547 5.4212 -1.42533 -0.581023 1 5.63547 5.42181 1.423 -0.581101 1 5.63547 -2.50314 5.41265 -0.586151 3 5.99217 -2.50544 -5.41162 -0.585854 3 5.99217 -5.41151 2.50552 -0.586554 3 5.99217 -5.41257 -2.50326 -0.586416 3 5.99217 2.50334 -5.41269 -0.585024 3 5.99217 2.50564 5.41159 -0.585321 3 5.99217 5.4117 -2.50555 -0.584622 3 5.99217 5.41277 2.50322 -0.584759 3 5.99217 -0.705001 6.62658 -0.692551 1 6.69987 -0.707815 -6.62632 -0.692187 1 6.69987 -6.62618 0.707911 -0.693369 1 6.69987 -6.62648 -0.705135 -0.69333 1 6.69987 0.70523 -6.62662 -0.691953 1 6.69987 0.708044 6.62628 -0.692316 1 6.69987 6.62641 -0.707949 -0.691134 1 6.69987 6.62671 0.705096 -0.691173 1 6.69987 -1.23945 7.56123 -0.780998 3 7.70184 -1.24266 -7.56074 -0.780583 3 7.70184 -7.56059 1.24277 -0.781872 3 7.70184 -7.56112 -1.2396 -0.781804 3 7.70184 1.23971 -7.56127 -0.780172 3 7.70184 1.24292 7.5607 -0.780587 3 7.70184 7.56085 -1.24281 -0.779298 3 7.70184 7.56138 1.23956 -0.779366 3 7.70184 END On Thu, 28 Aug 2008, ifeffit-request@millenia.cars.aps.anl.gov wrote:

1. Problem reproducing spectrum for Ti complex (Janine GRATTAGE)

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Message: 1 Date: Thu, 28 Aug 2008 10:42:31 +0200 From: Janine GRATTAGE Subject: [Ifeffit] Problem reproducing spectrum for Ti complex To: Ifeffit@millenia.cars.aps.anl.gov Message-ID: <48B664F7.6010704@esrf.fr> Content-Type: text/plain; charset="iso-8859-1"

Dear IFEFFIT mailing list,

I have been trying to reproduce the XANES spectrum of a titanium compound (titanium phthalocyanine dichloride) using FEFF 8.4. The overall shape is reproduced reasonably well, but I wanted to ask the mailing list users if they have any ideas as to how to improve the details such as the pre-edge (to give two distinct peaks) and peak positions over the absorption edge.

I have attached a file showing the experimental spectrum, two FEFF input files and the corresponding XMU output files. These two files have the same atomic co-ordinates for the molecule, but one has 'standard' broadening and the Fermi level has been shifted by -1eV (geom1) where the other has reduced experimental broadening (-3) a shifted Fermi level, and smaller step size (geom1acc).

I have tried changing the geometry of the molecule by moving one or both of the Cl atoms, and by trying a flat molecular geometry rather than the 'umbrella' shape in the attached files, but the spectra attached are the best match to experiment. Any help or suggestions on improvements would be greatly appreciated.

Best regards and thanks in advance,

Janine Grattage

-- Dr Janine GRATTAGE Postdoctoral Fellow, ID26 European Synchrotron Radiation Facility (ESRF) Sector 26, BP 220 6, rue Jules Horowitz, 38043 Grenoble, Cedex 9, FRANCE Tel: +33(0)4 38 88 19 30 Email: janine.grattage@esrf.fr