s tit
Gallium Antimonide (RT)
q
gs tab no
alias pcp;gs d p;cp;gs d t
alias pp;gs d p;p;gs d t
!
!Fitting of RT GaSb - cubic, sphalerite structure
!
!Read the data for the gallium edge
r ex 1
cgasb.exb
1
32
ga k



!Read the data for the antimony edge
r ex 2;csbga.exb;;32;sb k;;;;
!Read some pre-existing phaseshift files
r ph
6
exphsa1.gac
.sb;.ga;.sbc;.ga2;.sb2
!Generate the structure - this is made slightly more
!complicated by the need to generate two clusters
!First set the atom parameters for the first spectrum
c atom[1,3] ga;c atom2 sb
!Set the first shell distance to 6.095/sqrt(16/3) - the approximate
!crystallographic value at RT
c r1 2.63921
!Set the atom types for the first two shells and the cluster size
c t1 sb;c t2 ga;c ns 13
!define the structure
str sph q
l log
^rm par1
!store the result for the Ga edge
pr par
par1
!Repeat for the Sb edge - remember to redefine the central atom type
c atom5 ga;c atom[4,6] sb
c t0 4;c t1 ga;c t2 sb;str sph q
!Note that if all the atom types had all been defined initially,
!it would have been neccessary to use: c t1 2;c t2 3 for the
!Ga edge. It is in any case neccessary to use: C T0 4, not C T0 SB
l log
^rm par2
pr par;par2
!Now re-read the parameters for each cluster
r par;par1
r par add;par2
!Fix the cluster parameters for the second cluster
c clus14 -2;c clus[15-ns] 2
!Select the useful energy range
c emin 5;c emax 1250
!Make sure the point group (Td) is defined for both clusters
sym;td;td
!Select the MS parameters - 5th order but paths
!involve only 3 DIFFERENT scatterers - initially only include
!paths to 12 angstroms
c atmax 3;c omax 5;c plmax 12
!Turn the MS on
s ms al
!Select some initial DW factors
c a[1-ns] .02
c a[1,15] .005;c a[2-4,16-18] .015
!Two energy zero terms are also needed - set these to some value other
!than 0 at the start
c ef1 20;c ef2 1
l log
!Plot the result (this will be slow)
cp
!Refine the structure - as it is cubic, only ACELL can
!sensibly be refined - it will just scale all the distances
ref 80
acell
ef1
ef2
=
!This is correct so no editing needed
c
!The complete option will complete the refinement without further prompts
p;c;=
!Replot
cp
ref res 180;c;c;=
!Add some more MS paths
c plmax 16
!The DW factors for Ga-Sb and Sb-Ga at the same distance must be the same
!Here it is also assumed that Ga-Ga and Sb-Sb DW factors are the same
!(this turns out to be a reasonable approximation)
ref;a[1,15];a[2,16];a[3,17];a[4,18];a[5,19];a[6,7,20,21];a[8,9,22,23];=
!First cycle will be slow
c;p;c;
