Hi euG, That amp is not physically reasonable, unless you're using it as a proxy for the coordination number. The uncertainty on the other variables does not seem high to me for a single-shell fit. Well, 2 eV is a bit high for an uncertainty on E0, but not crazy high. There are some approaches that can be used to try to reduce the uncertainties, but you shouldn't even think about that until you get the amp (S02) straightened out. --Scott Calvin Sarah Lawrence College On Aug 18, 2009, at 6:18 PM, Eugenio Otal wrote:
Hi Scott, here I copy a part of the report:
Independent points = 6.222656250 Number of variables = 4.000000000 Chi-square = 247.145092496 Reduced Chi-square = 111.193574128 R-factor = 0.017422216
Guess parameters +/- uncertainties (initial guess): amp = 6.7815290 +/- 1.4687660 (1.0000) enot = 2.2173620 +/- 2.1499920 (0.0000) delr = 0.0514640 +/- 0.0163900 (0.0000) ss = 0.0074020 +/- 0.0025220 (0.0030)
I see that the R-factor is pretty good, 1.74%, amp is high cause is correlated with the coordination number and always have big errors., delr has the error of the total distance, so it is ok, but ss and enot have a a really big error, is this normal? Thanks, euG