Dear FEFF users,

Using FEFF8.4, I am trying to perform EXAFS calculations with rather large RMAX and NLEG values. The system of interest is graphite. It has been shown by Castrucci et al (J. Phys. Chem. C 2009, 113, 4848–4855), that convergence of the EXAFS modulations in the region 4-6 A-1 is only achieved for a cluster size of RMAX = 8 and including up to 8-body MS paths (NLEG = 8). I have tried to reproduce these calculations and noticed that the path finder runs into a limit when I use these parameters. I can maximally use RMAX = 7.5 and NLEG =  5. With larger RMAX or NLEG values I get the message:

"Internal path finder limit exceeded -- path list may be incomplete.",

and the cluster size subsequently truncated at 6-6.5 A (depending on NLEG), instead of the desired 8 A.

My path filter criteria are 3% (plane-wave) and 4% (curved-wave). However, these values do not affect the appearance of the above message, which occurs before the path filter is applied. Consequently, altering the 'npx' parameter, as suggested here http://leonardo.phys.washington.edu/feff/wiki/static/c/o/d/Code_Variables_and_Dimensions_ceec.html, does not help.

Is there a way to increase this internal path limit so I can work with RMAX = 8 and NLEG = 8? 

P.S.1 I guess graphite is a special case for which MS can be very efficient within the graphite planes. In addition, the C-C bond length is quite short, which makes higher n-body paths more important.

P.S.2 I have tried merging XANES and EXAFS using the cards: XANES, FMS 6, RPATH 8 and NLEG 8, but the same problem occurs and the agreement with experiment in the low-k region 3-6 A-1 does not become better using FMS (compared to the path expansion).

Thanks in advance,

Best wishes,

Renske