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