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     program feff (version 3.28)
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     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     input:  feff.inp   (see samples below)
c     output:  chi.dat   (and other files depending on print level)
c     NOTE: delete or rename old chi.dat and other.dat files 
c           prior to running
c Sample input files: (5 lines; 6 lines if options are specified)
c     NOTE: format is slightly chnaged from earlier versions
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 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   Description of input:
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   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   print  output file    file contents
c   level  
c    0   Standard xafs data chi(k) relative to threshold (angstroms)
c        chi.dat      k,  chi(k), |chi(k)|, ph(chi)  (xafs)
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        save.dat     phase shift data (binary file)
c        misc.dat     file header, used to identify run
c    2   Effective scattering amplitude and phase shift data, with k
c        referenced to threshold
c        feff.dat     k,  phi_c, |feff|,  ph(feff),
c                         so**2, lambda,  Re(p)
c    3   Theoretical curved wave xafs data for chi(p) relative to
c                the muffin-tin zero  (atomic units)
c        feffcw.dat   k, 2*real(delta_c), |fth|,   ph(fth), 
c                        so**2,   Re(p),  Im (p)
c    4   Theoretical plane wave xafs data for chi(p) relative to 
c                the muffin-tin zero  (atomic units)
c        feffpw.dat   k, 2*real(delta_c), |fpw|,   ph(fpw),
c                        so**2,   Re(p),   Im (p)
c    5   atom.dat      atom ground state data
c    10  phase.dat     atomic phase shifts
c   variables:
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     Machine and compiler requirements and installation notes: 
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     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     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     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  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 Main Authors: please constact us concerning any problems with the codes.
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 Citations: Please acknowledge the use of these codes in published work
c by citing at least one of the following articles:
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     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     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        version  1.0  (*)         preliminary versions of atom,
c                                  phase, and ssk xafs codes
c                                * see subroutines for dates
c        version  2.0  (9  aug 89) unified atom, phase, xafs codes
c                 2.1  (13 sep 89) modified output format
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     FEFF 3.28 copyright 1990 by the FEFF project at the University of
c     Washington.  All rights reserved.  See license information below.
c    Addendum: (DO NOT DELETE)
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     FEFF TABLES of XAFS phases and amplitudes and associated software
c     and a multiple shell code FEFF 4 are also available.
c     Government copyright notice: (DO NOT DELETE)
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)(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, 
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c     derivative works based thereon,
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c     (c)(2) The grantee agrees that it will not knowingly include any 
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