Riccardo,
There is a easier way to do this -- you can scale the two scans so they
are on a common scale, (be sure to scale the standard uncertainties by
the same factors). Then that the two scans can be placed in a single
histogram. You can then use the "ESD" input format (see p. 217 in the
GSAS manual) to read in the scaled points and the scaled standard
uncertainties.
If you do it in two histograms, you will get the identical result -- if
you fix the ratio of the scale factors.
Strictly speaking, you cannot combine R(F**2) values the way you want,
as
R(F**2) = SUM(|delta(F2)|) / SUM(F2obs)
where delta is obs-calc so
R(F**2)-total = [SUM(F2obs)(a)* R(F**2)(a) +
SUM(F2obs)(b)* R(F**2)(b)] /
[SUM(F2obs)(a) + SUM(F2obs)(b)]
perhaps you can get SUM(F2obs) from the RCALC program, or by adding the
values in REFLIST.
Brian
Riccardo Vivani wrote:
>
> Dear all,
> This is an example of the output for a GSAS cycle, using two histograms (two
> portions of a diffraction spectrum, with different step scan times)
>
> Powder data statistics Fitted -Bknd
> Average
> Bank Ndata Sum(w*d**2) wRp Rp wRp Rp DWd
> Integral
>
> Hstgm 1 PXC 1 5699 20672. 0.1295 0.1002 0.1275 0.0990 0.584
> 0.884
> Hstgm 2 PXC 1 2484 5798.1 0.0746 0.0600 0.0791 0.0618 0.887
> 0.887
> Powder totals 8183 26470. 0.1078 0.0818 0.1192 0.0871 0.650
> Cycle 319 There were 8183 observations.
> Total before-cycle CHI**2 (offset/sig) = 2.6470E+04 ( 1.4352E+02)
>
> Reduced CHI**2 = 3.249 for 35 variables
> Histogram 1 Type PXC Nobs= 222 R(F**2) = 0.0549
> Histogram 2 Type PXC Nobs= 602 R(F**2) = 0.0507
>
> I would know if it is possible to build a global R(F**2), for example
>
> {R(F**2)[1] x Nobs[1] + R(F**2)[2] x Nobs[2]} / {Nobs[1] + Nobs[2]} = 0.0518
>
> or some other procedure
>
> Thank you very much
> Riccardo Vivani
--
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Brian H. Toby, Ph.D. Leader, Crystallography Team
[EMAIL PROTECTED] NIST Center for Neutron Research, Stop 8562
voice: 301-975-4297 National Institute of Standards & Technology
FAX: 301-921-9847 Gaithersburg, MD 20899-8562
http://www.ncnr.nist.gov/xtal
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