[Ifeffit] Node in chi(k) envelope for a single shell
levy at msri.org
levy at msri.org
Sun Nov 5 06:38:56 CST 2006
Dear List,
I have noticed in several fits that Artemis -- i.e., feff -- reports for
a SINGLE shell (with absorber = scatterer = Hg, edge = L3) an almost-node
in the envelope of chi(k) around 6 inverse angstroms. See the image at
http://pjm.math.berkeley.edu/users/levy/files/HgNode.gif
and the FEFF output after my signature.
I've done my best to account for this behavior, but I simply don't
have a physical intuition for why the F(k) factor should dip to zero
or almost zero. Note that this is not a beat caused by two similar
frequencies being added; the Fourier transform does
of course show two peaks -- which is how my curiosity was aroused --
but the example figure comes from a SINGLE path, with 12 identical
scatterers all at the same distance from the absorber.
Looking forward to your two cents...
Silvio
Metacinnabar from CSDWeb, HgS Niculescu et al. 1970 Feff 6L.02 potph
4.12
Abs Z=80 Rmt= 1.327 Rnm= 1.667 LIII shell
Pot 1 Z=16 Rmt= 1.218 Rnm= 1.515
Pot 2 Z=80 Rmt= 1.310 Rnm= 1.624
Gam_ch=5.000E+00 H-L exch
Mu=-2.727E+00 kf=1.809E+00 Vint=-1.519E+01 Rs_int= 2.005
Path 2 icalc 2 Feff 6L.02
genfmt 1.4\4
------------------------------------------------------------------------------\-
2 12.000 4.1366 2.9707 -2.72701 nleg, deg, reff, rnrmav(bohr),
edge
x y z pot at#
0.0000 0.0000 0.0000 0 80 Hg absorbing atom
0.0000 -2.9250 -2.9250 2 80 Hg
k real[2*phc] mag[feff] phase[feff] red factor lambda
real[p]@#
0.000 5.8876E+00 0.0000E+00 -5.3100E+00 0.1085E+01 5.5410E+00
1.8179E+00
0.200 5.8828E+00 6.5887E-02 -6.9020E+00 0.1085E+01 5.5726E+00
1.8284E+00
0.400 5.8685E+00 1.3063E-01 -8.3679E+00 0.1084E+01 5.6628E+00
1.8594E+00
0.600 5.8452E+00 1.9388E-01 -9.7059E+00 0.1082E+01 5.7987E+00
1.9101E+00
0.800 5.8135E+00 2.5592E-01 -1.0913E+01 0.1079E+01 5.9607E+00
1.9793E+00
1.000 5.7742E+00 3.1673E-01 -1.1989E+01 0.1077E+01 6.1257E+00
2.0656E+00
1.200 5.7279E+00 3.7510E-01 -1.2932E+01 0.1075E+01 6.2715E+00
2.1679E+00
1.400 5.6750E+00 4.2855E-01 -1.3742E+01 0.1074E+01 6.3832E+00
2.2854E+00
1.600 5.6157E+00 4.7354E-01 -1.4416E+01 0.1075E+01 6.4589E+00
2.4174E+00
1.800 5.5491E+00 5.0618E-01 -1.4949E+01 0.1076E+01 6.5142E+00
2.5639E+00
2.000 5.4733E+00 5.2301E-01 -1.5329E+01 0.1077E+01 6.5837E+00
2.7250E+00
2.200 5.3844E+00 5.2240E-01 -1.5543E+01 0.1078E+01 6.7192E+00
2.9013E+00
2.400 5.2972E+00 5.4699E-01 -1.5605E+01 0.1190E+01 4.9983E+00
3.0942E+00
2.600 5.3179E+00 5.7289E-01 -1.5987E+01 0.1239E+01 4.3905E+00
3.2252E+00
2.800 5.3348E+00 5.8762E-01 -1.6217E+01 0.1258E+01 4.1537E+00
3.3638E+00
3.000 5.3246E+00 5.9586E-01 -1.6383E+01 0.1257E+01 4.0743E+00
3.5096E+00
3.200 5.3065E+00 6.1650E-01 -1.6474E+01 0.1250E+01 4.0802E+00
3.6618E+00
3.400 5.2733E+00 6.3374E-01 -1.6567E+01 0.1239E+01 4.1398E+00
3.8197E+00
3.600 5.2309E+00 6.4470E-01 -1.6663E+01 0.1226E+01 4.2364E+00
3.9827E+00
3.800 5.1752E+00 6.3603E-01 -1.6766E+01 0.1212E+01 4.3604E+00
4.1501E+00
4.000 5.1090E+00 6.0562E-01 -1.6883E+01 0.1198E+01 4.5058E+00
4.3214E+00
4.200 5.0331E+00 5.5941E-01 -1.6984E+01 0.1183E+01 4.6683E+00
4.4959E+00
4.400 4.9489E+00 4.9872E-01 -1.7115E+01 0.1168E+01 4.8452E+00
4.6734E+00
4.600 4.8588E+00 4.2625E-01 -1.7230E+01 0.1154E+01 5.0343E+00
4.8533E+00
4.800 4.7653E+00 3.5048E-01 -1.7327E+01 0.1139E+01 5.2341E+00
5.0355E+00
5.000 4.6691E+00 2.7395E-01 -1.7453E+01 0.1125E+01 5.4434E+00
5.2195E+00
5.200 4.5722E+00 1.9793E-01 -1.7590E+01 0.1110E+01 5.6610E+00
5.4051E+00
5.400 4.4760E+00 1.3243E-01 -1.7866E+01 0.1096E+01 5.8864E+00
5.5922E+00
5.600 4.3817E+00 8.0754E-02 -1.8387E+01 0.1083E+01 6.1187E+00
5.7805E+00
5.800 4.2890E+00 7.7722E-02 -1.9408E+01 0.1070E+01 6.3576E+00
5.9699E+00
6.000 4.1996E+00 1.2225E-01 -1.9952E+01 0.1058E+01 6.6024E+00
6.1603E+00
6.500 3.9822E+00 2.6906E-01 -2.0350E+01 0.1031E+01 7.2385E+00
6.6398E+00
7.000 3.7681E+00 3.8170E-01 -2.0473E+01 0.1010E+01 7.9052E+00
7.1233E+00
7.500 3.5495E+00 4.3899E-01 -2.0529E+01 0.9919E+00 8.5988E+00
7.6098E+00
8.000 3.3245E+00 4.4840E-01 -2.0549E+01 0.9763E+00 9.3169E+00
8.0987E+00
8.500 3.1062E+00 4.3705E-01 -2.0526E+01 0.9613E+00 1.0057E+01
8.5893E+00
9.000 2.8953E+00 4.1495E-01 -2.0476E+01 0.9480E+00 1.0818E+01
9.0814E+00
9.500 2.6939E+00 3.9247E-01 -2.0391E+01 0.9367E+00 1.1598E+01
9.5746E+00
10.000 2.4999E+00 3.7170E-01 -2.0271E+01 0.9291E+00 1.2396E+01
1.0069E+01
11.000 2.1169E+00 3.6890E-01 -1.9990E+01 0.9196E+00 1.4041E+01
1.1059E+01
12.000 1.7611E+00 4.1306E-01 -1.9816E+01 0.9119E+00 1.5747E+01
1.2052E+01
13.000 1.4328E+00 4.6749E-01 -1.9744E+01 0.9072E+00 1.7507E+01
1.3046E+01
14.000 1.1169E+00 5.1022E-01 -1.9760E+01 0.9054E+00 1.9317E+01
1.4041E+01
15.000 8.2534E-01 5.3666E-01 -1.9821E+01 0.9032E+00 2.1172E+01
1.5037E+01
16.000 5.5314E-01 5.4489E-01 -1.9903E+01 0.9025E+00 2.3070E+01
1.6034E+01
17.000 2.9163E-01 5.3763E-01 -2.0012E+01 0.9015E+00 2.5007E+01
1.7031E+01
18.000 4.7223E-02 5.2008E-01 -2.0124E+01 0.8986E+00 2.6981E+01
1.8029E+01
19.000 -1.8906E-01 4.9327E-01 -2.0255E+01 0.8968E+00 2.8989E+01
1.9027E+01
20.000 -4.1335E-01 4.6035E-01 -2.0384E+01 0.8947E+00 3.1029E+01
2.0025E+01
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