Calculation of xray absorption spectra

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Calculation of x-ray absorption spectra

• Christian Brouder
• Institut de Minéralogie et de Physique des
  Milieux Condensés

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Theoretical approaches
A bit of history One body Two bodies Many bodies
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The malediction of XAFS calculations
Kronig (1931) Petersen (1932) Bogdanovich
(1937) Natoli (1980)
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The main approaches
One-body calculation
Two-body calculations
Many-body calculations
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One-body
s(E) 4p2a E Snltfne.rf0gt2 d(en-e0-E) (-D
V(r)) fn(r) en fn(r) V VcVxc DFT LDA
Kohn-Sham V VcS Green function
theory f0(r) core-hole wavefunction
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Multiple-scattering theory
Indras net Avatamsaka sutra
The book of Buddha garlands (400) Lord Rayleigh
(1892) Kasterin (1897) Korringa (1945,1947) Kohn
Rostoker (1953)
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The muffin-tin approximation
Spherical atoms in a constant interstitial
potential
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The muffin-tin approximation
Spherical atoms in a constant interstitial
potential
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Muffin-tin programs
CONTINUUM (Natoli, 1980) ICXANES (Durham et al.,
1982) http//cpc.cs.qub.ac.uk/summaries/AAR
R.html FEFF8 (Rehr et al., 1991)
http//leonardo.phys.washington.edu/feff/ SPRKKR
(Ebert et al., 1998) relativistic
olymp.cup.uni-muenchen.de/ak/ebert/SPRKKR/ MXAN
(Benfatto et al., 2002)
maurizio.benfatto_at_lnf.infn.it PY-LMTO (Antonov et
al., 2001) relativistic LMTO
yaresko_at_mpipks-dresden.mpg.de
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Non muffin-tin

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Non-muffin-tin programs
FPX (Foulis, 1986-2002) Non-muffin-tin
multiple scattering www.esrf.fr/computing/scie
ntific/fpx/fpx.htm WIEN2k (Blaha et al., 1998)
FP-LAPW www.wien2k.at/ FDMNES (Joly, 2001)
Finite difference method 147.173.148.95/LDC/LE
_LABORATOIRE/Equipes_de_recherche/EQUIPE_SPECTROSC
OPIE/SIMUL/EtudFond_Prog.asp

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Non-muffin-tin programs
PARATEC (Cabaret et al., 2002)
pseudopotential www-ext.lmcp.jussieu.fr/cabare
t/xanes.html EXC!TING (Dewhurst et al., 2006)
FP-LAPW exciting.sourceforge.net/ STOBE
(Saint-Amant et al., 1992) LCAO
www.fhi-berlin.mpg.de/th/th.html

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Two-body
Bethe-Salpeter LL0L0KL L0(1212)G(1,2)G(2,1
) The dielectric response ?(x,y) ?
lt0j(x),j(y)0gt can be obtained from L
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BS TDDFT programs
ADF (Stener et al., 2003) TDDFT
www.scm.com/ DP (Olevano et al., 1999) TDDFT
pseudopotential theory.polytechnique.fr/codes/d
p/dp.html EXC Bethe-Salpeter pseudopotential
theory.polytechnique.fr/codes/exc/exc.html NBSE
(Shirley, 1998) Bethe-Salpeter
pseudopotential physics.nist.gov/Divisions/Div8
44/staff/Gp4/shirley.html

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Many-body
Many-body states
s(E) 4p2a E SnltFne.rF0gt2 d(en-e0-E) (-D
SiVn(ri) SijVe(rij)) Fngt en Fngt F0gt
many-body ground state
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Multiplet programs
TT-MULTIPLETS (Thole et al., 1990)
www.anorg.chem.uu.nl/people/staff/FrankdeGroot/ttm
ultiplets.htm/ Cluster (Kotani et al., 1992)
theo.phys.okayama-u.ac.jp/okada/index_e.html/
AMARCORD (Mirone, 2000) www.esrf.fr/computing/
scientific/people/mirone/amarcord/

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Problems
Green functions and KS-(TD)DFT One-particle
orbitals are occupied or not Restricted to
closed shell systems Multiplets parametrized
very small systems

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Unifying approaches
Multichannel multiple scattering Krüger and
Natoli (2004) TDDFT for open shells in
progress (E.K.U Gross and coll.) Green functions
with correlation in progress

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Long-term program
CORRELATION