The accuracy of Reitveld analysis reflects on thevalue of chi^2...

yeah but what about standard deviation?

In the Rietveld refinement the values of refined lattice parameters with standard deviation are given in the output file. During reporting lattice parameters along with standard deviation you have to follow rules of significant figure. E.g. if

a=5.26657 +- 0.000236

b=6.23614 +- 0.000694

c=12.65469 +- 0.002152

Then you can report the results as

a=5.2666(2)

b=6.2361(7)

c=12.6547(21)

or

a=5.267(0)

b=6.236(0)

c=12.655(2)

I hope this may be helpful for you.

thank you so much! it is really helpful to me.