Here is an example of atoms in action. The material is Lead
Titanate, PbTiO3. The crystallographic literature places this material
in the tetragonal space group P 4 M M. The data was taken in
fluorescence at the titanium K-edge. Since the edge energy is around
5 KeV and the sample was very thick, the I0 and self-absorption
corrections are expected to be significant. That titanium is the
central atom is indicated by the keyword core. atoms
assumes the K-edge of the titanium was probed because the atomic
number of titanium is less than 57 and the edge was not otherwise
chosen with the edge keyword. The I0 chamber was filled with
92% helium and 8% nitrogen by pressure. This is
indicated by the nitrogen keyword. The indexing feature is
engaged with the index keyword. The size of the cluster to be
printed in feff.inp is chosen with the rmax keyword.
title PbTiO3 10K,a=3.885,c=4.139
space P 4 m m
a=3.885 c=4.139 nitrogen = 0.08
index=true rmax=4.2 core=ti
atom
! At.type x y z tag
Pb 0.0 0.0 0.0
Ti 0.5 0.5 0.5377
O 0.5 0.5 0.1118 axial
O 0.0 0.5 0.6174 planar
-------------------------------------------------
atoms produces the output reproduced below. The absorption and
correction calculations are at the top of the file. All the
CONTROL cards are set to 1 and the PRINT cards are set to 0.
This will run all four modules of feff and produce the default
output files. Several other useful feff cards are printed but
commented out by an asterisk (*). The unique potential list is
constructed in a simple fashion -- the core atom is potential 0 and
each different atomic species has a single potential. The atom list
is printed in the format required by feff. The atom list has two
comment columns. The indexed atomic symbol and radial distance are
written by atoms for your use when reading feff.inp and are
ignored by feff.
feff will run to completion using the input file generated by
atoms. It is still likely that the user will want to edit
feff.inp. Several assumptions are made by atoms
that might not hold true. The assignment of unique potentials is made
by a simple algorithm and may not adequately reflect the physics of
the problem. The CONTROL cards are such that all four modules of
feff will be run. The feff user might want to run
the modules separately. Values for other cards have been assumed and
might not be desired. Other cards have been left out entirely.
Always check your feff.inp file to be sure it is just
what you want.
* This feff.inp file generated by ATOMS, version 2.44a
* ATOMS written by Bruce Ravel and copyright of The Univ. of Washington, 1994
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
* total mu = 5269.6 cm^-1, delta mu = 772.6 cm^-1
* specific gravity = 8.057, cluster contains 123 atoms.
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
* mcmaster corrections: .00093 ang^2 and .165E-05 ang^4
* self-abs. corrections: amplitude factor = 1.087
* .00004 ang^2 and .461E-07 ang^4
* i0 corrections: .00118 ang^2 and .122E-05 ang^4
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
* sum of corrections: .00216 ang^2 and .292E-05 ang^4
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
TITLE PbTiO3 10K a=3.885 c=4.139
HOLE 1 1.0 Ti K edge ( 4.965 keV), s0^2=1.0
* mphase,mpath,mfeff,mchi
CONTROL 1 1 1 1
PRINT 0 0 0 0
RMAX 4.139
*CRITERIA curved plane
*DEBYE temp debye-temp
*NLEG 8
*XANES
POTENTIALS
* ipot z label
0 22 Ti
1 8 O
2 82 Pb
3 22 Ti
ATOMS
.00000 .00000 .00000 0 Ti_00 .00000
.00000 .00000 -1.76280 1 axial_01 1.76280
1.94250 .00000 .32988 1 planar_01 1.97031
.00000 1.94250 .32988 1 planar_01 1.97031
-1.94250 .00000 .32988 1 planar_01 1.97031
.00000 -1.94250 .32988 1 planar_01 1.97031
.00000 .00000 2.37620 1 axial_02 2.37620
1.94250 -1.94250 1.91346 2 Pb_01 3.34783
-1.94250 -1.94250 1.91346 2 Pb_01 3.34783
-1.94250 1.94250 1.91346 2 Pb_01 3.34783
1.94250 1.94250 1.91346 2 Pb_01 3.34783
1.94250 1.94250 -2.22554 2 Pb_02 3.53548
-1.94250 -1.94250 -2.22554 2 Pb_02 3.53548
-1.94250 1.94250 -2.22554 2 Pb_02 3.53548
1.94250 -1.94250 -2.22554 2 Pb_02 3.53548
.00000 3.88500 .00000 3 Ti_01 3.88500
-3.88500 .00000 .00000 3 Ti_01 3.88500
.00000 -3.88500 .00000 3 Ti_01 3.88500
3.88500 .00000 .00000 3 Ti_01 3.88500
.00000 .00000 4.13900 3 Ti_02 4.13900
.00000 .00000 -4.13900 3 Ti_02 4.13900
END
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