Hi Pushkar,

On Mon, Nov 23, 2015 at 11:28 PM, pushkar shejwalkar <pshejwalkar2004@gmail.com> wrote:

Dear Matt,
Thank you very much for your response. One more question. What value of corelation is acceptable/publishable?

A correlation > 0.999 is probably an indication of duplicate parameters in a model, but it's common to publish parameters (say, N and sigma2 or E0 and R) that are correlated by more than 0.9. The correlation simply measures the amount by which a parameters best-fit value would change if another parameter was changed away from its best-fit value. The uncertainties take these correlations into account.

also having a correlation number means the fit is not finished and I should change the values of variable that are correlated? is that so?

No. The fit is (or "can be") finished. The reported best-fit values are really the best values found, and the reported uncertainties are those that increase the best chi-square by reduced chi-square, taking into account the correlation. The correlation does not indicate a bad model or a bad fit, it's just a consequence of the complex model and limited data for XAFS.

Hope that helps,

--Matt