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Modifications in the INPUT_XSPECTRA instruction file: 

1) Changed the citation to Gougoussis et al.

2) Additional informations concerning the extraction of the core
   wavefunction are included.

MCB


git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@6590 c92efa57-630b-4861-b058-cf58834340f0
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calandra 2010-04-02 04:14:53 +00:00
parent c1b2b30add
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1 changed files with 31 additions and 15 deletions
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46
Doc/INPUT_XSPECTRA
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@ -8,7 +8,7 @@ described in:
Christos Gougoussis, Matteo Calandra, Ari P. Seitsonen, Francesco Mauri,
"First principles calculations of X-ray absorption in an ultrasoft
pseudopotentials scheme: from $\alpha$-quartz to high-T$_c$ compounds",
arXiv:0906.0897
Phys. Rev. B 80, 075102 (2009)
you should cite this work in all publications using this software.
@ -29,13 +29,18 @@ C. Gougoussis, M. Calandra, A. Seitsonen, Ch. Brouder, A. Shukla, F. Mauri
Finally you should cite properly the Quantum Espresso package.
-----------------------------------------------------------------------
XSpectra is a post-processing tools that relies on the output (the charge density)
of the PWscf code (pw.x). Thus a scf calculation needs to be done before running
XSpectra is a post-processing tools that relies on the output
(the charge density) of the PWscf code (pw.x).
Thus a scf calculation needs to be done before running
xspectra.x.
To simulate core-hole effects, a pseudopotential with a hole in the 1s
state needs to be generated for the absorbing atom. Some of these
pseudopotentials are available in the Xspectra examples directory.
To simulate core-hole effects, a pseudopotential with a hole in the s
state (1s for K-edges, 2s for L1-edges,...) needs to be generated
for the absorbing atom. Some of these
pseudopotentials are available in the Xspectra examples directory,
some other qre available on the QE pseudopotential web-page with the
label "*star1s*_gipaw*" for K-edges, "*star2s*_gipaw*" for L1-edges and so on.
The self-consistent calculation is then performed on a supercell including
the absorbing atom. The size of the supercell needs to be verified from
system to system, since fairly large supercells are necessary for convergence.
@ -52,7 +57,7 @@ The use of a single projector is discouraged, particularly when semicore
states are present. If more then two projectors are used, linear independence
of the projectors should be explicitly verified (verbosity='high').
Once the scf charge density has been obtained the xspectra.x code can be
Once the scf charge density has been obtained, the xspectra.x code can be
used as a post-processing tool. Note that the X-ray absorption spectra
can be calculated on a larger mesh, different from that used in the
PWscf scf run. Convergence need to be tested also for this second mesh.
@ -60,12 +65,20 @@ Xspectra calculates then the XAS dipolar or quadrupolar contributions
using the lanczos method and the continued fraction.
This approach does not require the explicit calculation of empty states
and it is consequently very fast (only the charge density is needed).
The code needs the 1s radial core wavefunction (for the 1s state in the absence of a
core-hole) in input. This is necessary to calculate the XAS matrix element.
The code needs the 1s radial core wavefunction
(for the 1s state in the absence of a
core-hole) in input. This wavefunction is included in the pseudo
and can be extracted using the script upf2plotcore.sh
in the directory ~/Pw/qe-forge/espresso/XSpectra/
of the QE distribution. Note that this script works only for UPF
version 1.
This is necessary to calculate the XAS matrix element.
The output spectrum can be separated in its spin-up and spin-down polarizations.
The output spectrum can be separated in its spin-up and
spin-down polarizations.
DFT+U calculations and collinear magnetism are possible.
Ultrasoft pseudopotentials are allowed.
Soon K-edge XMCD will be included in the package.
--------------------------------------------------------------------------
@ -249,14 +262,17 @@ r_paw(1:...) real(DP) DEFAULT=1.5*rc
In order to cut the occupied states, the program performs an integration
over the variable t in ] 0, infinity [.
See ref. Ch. Brouder, M. Alouani, K. H. Bennemann, Phys. Rev. B 54 (1996) p.7334-49.
For more details see ref.
Ch. Brouder, M. Alouani, K. H. Bennemann, Phys. Rev. B 54 (1996) p.7334-49.
The integration is done with t going in two opposite directions,
from the start value cut_startt. So, the integration
is done over ]cut_tinf,cut_startt] at least with step cut_stepl, and
over [cut_startt,cut_tsup[ at least with step cut_stepu. There are two arrays of size
cut_nmeml and cut_nmemu in order to save green functions values. There is an area near
the fermi level f size cut_desmooth (in eV) where the cross section is interpolated
in order to avoid a divergence.
over [cut_startt,cut_tsup[ at least with step cut_stepu.
There are two arrays of size
cut_nmeml and cut_nmemu
in order to save green functions values. There is an area near
the fermi level f size cut_desmooth (in eV) where the cross section
is interpolated in order to avoid a divergence.
NAMELIST / cut_occ /