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Documentation: Feff 3.28
Feff 3.28
The only documentation for Feff 3.28, a code for calculating phase shifts and scattering amplitudes for the elements suitable as single scattering standards, is the comments from the source code. These are reproduced below:
c-----------------------------------------------------------------------
c
c program feff (version 3.28)
c
c
c calculates ab initio single-scattering, curved wave xafs spectra,
c phase shifts and effective scattering amplitudes
c for arbitrary pairs of atoms throughout the
c periodic table (Z < 95)
c
c features: code uses a relativistic dirac-fock-slater desclaux
c atom code with the von barth-hedin ground state lda
c exchange correlation potential; scattering states are
c calculated using overlapped atom potentials (mattheiss
c prescription) plus a hedin-lundqvist complex exchange
c correlation potential for excited states, referenced
c to the averaged interstitial potential; muffin-tin
c radii are determined automatically from calculated
c norman radii; xafs spectra are referenced to the
c threshold fermi level, as determined by electron gas
c theory; atomic configurations and core-hole lifetimes
c are built in, and mean free paths are determined from
c the imaginary part of the avg interstitial potential
c
c input: feff.inp (see samples below)
c
c output: chi.dat (and other files depending on print level)
c
c NOTE: delete or rename old chi.dat and other.dat files
c prior to running
c
c Sample input files: (5 lines; 6 lines if options are specified)
c NOTE: format is slightly chnaged from earlier versions
c
c Copper K-shell 300K So**2=0.85 (title)
c 29 29 1 Z0, Z1, hole-code (atomic #'s, hole-code)
c 2.5526 12.0 12.0 rnn, nnn0, nnn1 (near-neigh dist, coord #'s)
c 0.00793 0.85 sigma2, s02 (DW and amplitude red. factors)
c 1 0 0 iprint, runflag, ioption
c
c SF6, 10% overlapping muffin-tins (title)
c 16 9 1 Z0, Z1, hole-code
c 1.56 6.0 1.0 rnn, nnn0, nnn1
c 0.001729 1.0 sigma2, s02
c 1 1 1 iprint, runflag, ioption
c 0 0 0 1.1 0.0 index_xc, ion0, ion1, folp, gamach
c
c Description of input:
c
c Subscript 0 refers to the absorbing atom, 1 to the backscatterer
c Distances are in Angstroms; energies in eV. Default entries are
c 0 or 0.0. For further details and definitions see the notes below.
c
c First line of this input file is the title of the run.
c Z0, Z1 Atomic numbers of absorbing and scattering atoms
c hole code 1 - K shell absorption
c 2 - LI shell
c 3 - LII shell
c 4 - LIII shell
c rnn Near neighbor distance (Angstroms)
c nnn0, nnn1 Coordination number of absorbing and scattering atoms
c NOTES: These coordination numbers are needed only to approximate
c coordination chemistry effects on the scattering
c potentials. Approximate values may be used.
c sigma2 Debye-Waller factor
c s02 Amplitude reduction factor; can be combined with nnn0 as
c an XAFS scale factor.
c iprint 0 - chi.dat only
c 1 - add misc.dat, save.dat
c 2 - add feff.dat
c ... (see below)
c 10 - all .dat files
c runflag 0 - Complete FEFF run using this input file
c 1 - Calculate only final XAFS results from previously
c calculated potentials and phase shifts. Useful if
c you want to modify Debye-Waller factor or rnn
c somewhat. Read new rnn, sigma2 and s02 from
c feff.inp, all phase shifts, etc., from save.dat.
c 2 - Used to generate FEFF TABLES of scattering amplitudes
c phase shifts, etc. (disabled in FEFF 3.28)
c ioption 0 - No special options
c 1 - Read option line containing the optional variables
c index_xc, ion0, ion1, folp, and gamach.
c WARNING: These options have been retained primarily for
c diagnostic purposes. Their use in most XAFS
c calculations is strongly discouraged. In particular the
c ionization cannot be interpreted as a chemical valence.
c We recommend that i_option be set to zero or that the
c default values 0 or 0.0 be used for all optional
c variables.
c index_xc 0 - Hedin-Lundquist exchange correlation potential
c 1 - Dirac-Hara
c ion0, ion1 Ionization of absorbing and scattering atoms.
c folp Overlapping muffin tins. folp=1.1 is 10% overlap, etc.
c gamach Core-hole width (eV). 0.0 for default
c
c print output file file contents
c level
c
c 0 Standard xafs data chi(k) relative to threshold (angstroms)
c
c chi.dat k, chi(k), |chi(k)|, ph(chi) (xafs)
c
c 1 Data to run calculation of chi, etc. only -- useful if
c only Debye-Waller factor, S02 or small changes to rnn are
c necessary.
c
c save.dat phase shift data (binary file)
c misc.dat file header, used to identify run
c
c 2 Effective scattering amplitude and phase shift data, with k
c referenced to threshold
c
c feff.dat k, phi_c, |feff|, ph(feff),
c so**2, lambda, Re(p)
c
c 3 Theoretical curved wave xafs data for chi(p) relative to
c the muffin-tin zero (atomic units)
c
c feffcw.dat k, 2*real(delta_c), |fth|, ph(fth),
c so**2, Re(p), Im (p)
c
c 4 Theoretical plane wave xafs data for chi(p) relative to
c the muffin-tin zero (atomic units)
c
c feffpw.dat k, 2*real(delta_c), |fpw|, ph(fpw),
c so**2, Re(p), Im (p)
c
c 5 atom.dat atom ground state data
c
c 10 phase.dat atomic phase shifts
c
c variables:
c
c k = wave number (ang**-1); k=sqrt(e-e_f) where
c e is energy and e_fermi is the fermi level
c computed from electron gas theory at the
c avg interstitial charge density
c chi(k) = so**2 * nnn0 * (|feff|/kR**2) * exp(-2R/lambda)
c * exp(-2k**2*sigma**2) * sin(2kR + ph(feff) + phi_c))
c (curved wave K or L-shell xafs function)
c phi_c = 2*delta_l_c -l*pi (total central atom phase)
c feff = effective, curved-wave backscattering amplitude
c feff(k) in xafs formula
c ph(feff) = phase of feff(k)
c fth = theoretical effective backscattering amplitude
c fth(p) = (k/p) feff(k) exp(2i (p-k) R)
c so**2 = S0**2*exp(-2 imag (delta_c) )
c total central atom loss factor
c R=rnn = near neighbor distance
c nnn0 = mean number of near neighbors to central atom
c sigma**2 = mean square variation of R
c lambda = mean free path (angstroms) =-1./imag (p)
c kf = fermi momentum at avg interstitial charge density
c p=p(r) = local momentum (p(r)**2=k**2+kf(r)**2+sigma-sigma_f)
c sigma = self energy at energy e, sigma_f at energy e_f
c
c Machine and compiler requirements and installation notes:
c
c The authors have endeavored to make FEFF portable to most
c machines without any modification. If your machine does not
c reproduce the test output files chi.dat and feff.dat to high
c accuracy, some changes may be needed. Please report any problems
c or warning messages to the authors. If changes are needed, keep
c in mind the following points:
c
c Floating point calculations must be done to precision 64 bits.
c Thus the code uses double precision variables throughout, i.e.,
c real*8 for real numbers and complex*16 for complex numbers. A
c single precision version for 64 bit word machines, e.g., CRAY and
c CDC, is also available from the authors.
c
c Code is written in ANSI FORTRAN 77, EXCEPT that complex*16
c variables are required. Since data type COMPLEX*16 is not part
c of the ANSI standard, minor compiler-dependent modification may
c be necessary. We have used the VAX extensions to ANSI FORTRAN 77
c since they seem to be the most portable. The non-standard
c statements and intrinsic functions used are: COMPLEX*16
c variables and arrays; DIMAG(arg) returns a double precision
c imaginary part of arg; DCMPLX(arg) returns a complex*16 version
c of arg; DBLE(arg) returns a double precision real part of arg;
c SQRT, EXP, ABS and other generic math functions are
c assumed to accept complex*16 arguments and return double
c precision or complex*16 results.
c
c Files are opened with the OPEN statement. As the ANSI definition
c gives some leeway in how the OPEN statement interacts with the
c operating system, we have chosen file names and conventions that
c work on UNIX, VAX/VMS, IBM PCs (and clones) with MS FORTRAN,
c CRAY, and CDC machines. It may be necessary to modify the open
c statements on other systems. All open statements are in the
c subroutine RDINP.
c
c Plotting output: utilities available from authors for
c ibm pc's, TopDrawer, conversion to UW XAFS format
c conversion of feff.dat to chi.dat, etc.
c
c
c Main Authors: please constact us concerning any problems with the codes.
c
c S. I. Zabinsky, U. Washington,
c zabinsky@uwaphast.bitnet (206) 543 0435
c J. J. Rehr, U. Washington,
c jjr@leonardo.phys.washington.edu (206) 543 8593
c R. C. Albers, Los Alamos,
c rca@nidhug.lanl.gov (505) 665 0417
c J. Mustre de Leon, Los Alamos,
c mustre@meediv.lanl.gov (505) 665 4008
c
c Citations: Please acknowledge the use of these codes in published work
c by citing at least one of the following articles:
c
c 1) J.J. Rehr, J. Mustre de Leon, S.I. Zabinsky, and R.C. Albers,
c J. Am. Chem. Soc. 113, 5135 (1991) (general description)
c 2) J. Mustre de Leon, J.J. Rehr, S.I. Zabinsky, and R.C. Albers,
c Phys. Rev. Bxx, xxxx (1991). (Sept 1 issue) (long write-up)
c
c RESTRICTIONS: feff is copyrighted software and a license must
c be obtained for its use. both academic/non-profit and corporate
c licenses are available - see the addendum to this document
c for details. new users should request the latest version of this
c code from the authors.
c
c acknowledgements: early versions of the exchange-correlation
c codes were written by d. lu; a. djaoui assisted with the
c complex version of the phase program; the atomic code is a
c automated version of the desclaux code (see subroutine atom)
c we also thank many users of early versions of this code,
c especially, m. benfatto, s. cramer, c.r. natoli, d. sayers,
c e.a. stern, and t. tyson for comments and suggestions.
c
c version 1.0 (*) preliminary versions of atom,
c phase, and ssk xafs codes
c * see subroutines for dates
c
c version 2.0 (9 aug 89) unified atom, phase, xafs codes
c 2.1 (13 sep 89) modified output format
c
c version 3.0 (14 feb 90) new version with overlapping atom
c potential and muffin-tin finder
c 3.1 (28 mar 90) four-point integration added for
c potentials, minor coding changes
c to enhance portability
c 3.23 (24 jul 90) minor bugs fixed, save.dat added
c (2 oct 90) gov't copyright notice added
c 3.24 (21 oct 90) interstitial avgs modified
c 3.25 (26 dec 90) minor modifications to enhance
c portability, minor dirac-hara fix
c 3.28 (12 sep 91) various minor bug fixes
c-----------------------------------------------------------------------
c
c FEFF 3.28 copyright 1990 by the FEFF project at the University of
c Washington. All rights reserved. See license information below.
c
c----------------------------------------------------------------------
c Addendum: (DO NOT DELETE)
c
c FEFF is copyrighted software and users must obtain a license
c for its use from the Univ. of Washington Office of Technology
c Transfer. The license may be obtained by writing to FEFF Project,
c c/o Marion Joyner, Dept. of Physics, FM-15, Univ. of Washington,
c Seattle, WA 98195. Tel: (206) 685-2400 or e-mail to
c joyner@newton.phys.washington.edu
c
c FEFF TABLES of XAFS phases and amplitudes and associated software
c and a multiple shell code FEFF 4 are also available.
c
c----------------------------------------------------------------------
c Government copyright notice: (DO NOT DELETE)
c
c This work was supported in part by DOE Grant DE-FG06-90ER45416.
c In accordance with the DOE FAR rules part 600.33 "Rights in
c Technical Data - Modified Short Form" the following clause
c applies to FEFF:
c
c (c)(1)The grantee agrees to and does hereby grant to the
c Government and to others acting on its behalf:
c (i) A royalty-free, nonexclusive, irrevocable, world-wide
c license for Governmental purposes to reproduce, distribute,
c display, and perform all copyrightable material first produced or
c composed in the performance of this grant by the grantee, its
c employees or any individual or concern specifically employed or
c assigned to originate and prepare such material and to prepare
c derivative works based thereon,
c (ii) A license as aforesaid under any and all copyrighted or
c copyrightable work not first produced or composed by the grantee
c in the performance of this grant but which is incorporated in the
c material furnished under the grant, provided that such license
c shall be only to the extent the grantee now has, or prior to
c completion or close-out of the grant, may acquire the right to
c grant such license without becoming liable to pay compensation to
c others solely because of such grant.
c (c)(2) The grantee agrees that it will not knowingly include any
c material copyrighted by others in any written or copyrightable
c material furnished or delivered under this grant without a
c license as provided for in paragraph (c)(1)(ii) of this section,
c or without the consent of the copyright owner, unless it obtains
c specific written approval of the Contracting Officer for the
c inclusion of such copyright material.
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BR