<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px"><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr">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".</div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr"><br></div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr">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 sig).</div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr"><br></div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr">It seems that Gsas is computing "gam" with different values of X and Y than the ones showing on "Instrument Parameters". Help please!</div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr"><br></div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr">Thanks in advance,</div><div id="yui_3_16_0_1_1415383213635_2440" dir="ltr">Cássio M. dos Santos</div></div></body></html>