I performed a refinement for LaB6 and the X, Y instrument parameters seems to 
be wrong. I got the values X=1.848 and Y=-4.186 and when substituted in the 
equation gam = X/cos(theta) + Y*tan(theta) it returns negative values for 
2theta > 53 degrees. The values calculated with the equation above are also 
different from the ones listed in the gam column of the "Reflection Lists".
I also noted that the values for U, V and W do match the ones in the "sig" 
column of the "Reflection lists" (using U*tan^2(theta) + V*tan(theta) + W for 
It seems that Gsas is computing "gam" with different values of X and Y than the 
ones showing on "Instrument Parameters". Help please!
Thanks in advance,Cássio M. dos Santos
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