These cards in this section are not associated with any particular module, but are used throughout the FEFF calculation. The ATOMS card is used to specify the absorbing atom and its environment. (If atomic coordinates are not known, then the OVERLAP card can be used to construct approximate potentials). Without this structural information no calculations can be done. The CONTROL card is used to selectively run parts of FEFF. The PRINT card controls which output files are written by the modules.
ATOMS * x y z ipot SF6 molecule 0.0 0.0 0.0 0 S K-shell hole 3.61 0.00 0.00 1 F 1st shell atoms 0.00 3.61 0.00 1 0.00 0.00 3.61 1 -3.61 0.00 0.00 1 0.00 -3.61 0.00 1 0.00 0.00 -3.61 1
CONTROL ipot ixsph ifms ipaths igenfmt iff2chi (Standard)
* example 1 * calculate self consistent potentials, phase shifts and fms only CONTROL 1 1 1 0 0 0 ipot ixsph ifms ipaths igenfmt iff2chi * example 2 * run paths, genfmt and ff2chi; do not run pot, xsph, fms * this run assumes previous modules have already been run and * adds MS paths between rfms and rpath to the MS expansion CONTROL 0 0 0 1 1 1 ipot ixsph ifms ipaths igenfmt iff2chi
PRINT ppot pxsph pfms ppaths pgenfmt pff2chi (Standard)
* add crit.dat and feffNNNN.dat files to minimum output PRINT 0 0 0 1 0 3The print levels for each module are summarized in Table 2.1 on page .
Table 2.1: Print levels controlling output files from the modules.
TITLE title_line (Standard)
TITLE Andradite (Novak and Gibbs, Am.Mineral 56,791 1971) TITLE K-shell 300K
END ignore any lines in feff.inp that follow this card
RMULTIPLIER rmult (Useful)
*increase distances by 1% RMULTIPLIER 1.01
CFAVERAGE iphabs nabs rclabs (Advanced)
A ``configuration'' average over absorbers is done if the CFAVERAGE card is given. CFAVERAGE currently assumes phase transferability, which is usually good for EXAFS calculations, but may not be accurate for XANES. Note that the CFAVERAGE card is currently incompatible with the NOGEOM card and with the DEBYE card for options other than correlated Debye model ().
*average over all atoms with iph=2 in feff.inp with less than 1000 atoms CFAVERAGE 2 0 0
OVERLAP iph (Advanced)
The OVERLAP card can be used to construct approximate overlapped atom potentials when atomic coordinates are not known or specified. If the atomic positions are listed following the ATOMS cards, the OVERLAP cards are not needed. FEFF8 will stop if both ATOMS and OVERLAP cards are used. The OVERLAP card contains the potential index of the atom being overlapped and is followed by a list specifying the potential index, number of atoms of a given type to be overlapped and their distance to the atom being overlapped. The examples below demonstrate the use of an OVERLAP list. This option can be useful for initial single scattering XAFS calculations in complex materials where very little is known about the structure.
You should verify that the coordination chemistry built in using the OVERLAP cards is realistic. It is particularly important to specify all the nearest neighbors of a typical atom in the shell to be overlapped. The most important factor in determining the scattering amplitudes is the atomic number of the scatterer, but the coordination chemistry should be approximately correct to ensure good scattering potentials. Thus it is important to specify as accurately as possible the coordination environment of the scatterer. Note: If you use the OVERLAP card then you cannot use the FMS or SCF cards. Also the pathfinder won't be called and you must explicitly specify single scattering paths using SS card, which is described in Section 2.6.
* Example 1. Simple usage * Determine approximate overlap for central and 1st nn in Cu OVERLAP 0 determine overlap for central atom of Cu *iphovr novr rovr * ipot, number in shell, distance 1 12 2.55266 OVERLAP 1 determine approximate overlap for 1st shell atoms *iphovr novr rovr * ipot, number in shell, distance 0 12 2.55266 * Example 2. More precise usage * Determine approximate overlap for 3rd shell atoms of Cu OVERLAP 3 0 1 2.55266 ipot, number in shell, distance 1 4 2.55266 2 7 2.55266 2 6 3.61000 2 24 4.42133