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--></style></head><body lang=EN-US link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span class=DefaultFontHxMailStyle>Dear GSAS-II users,<o:p></o:p></span></p><p class=MsoNormal><span class=DefaultFontHxMailStyle><o:p> </o:p></span></p><p class=MsoNormal><span class=DefaultFontHxMailStyle>I am refining a synchrotron’s pattern of intercalated FeSe sample named LiPyFeSe, with Pnma space group. I’ve tried to use the </span><span class=DefaultFontHxMailStyle><b>generalized microstrain</b> model which well-fits couple of the high-Q peaks which the isotropic model doesn’t. BUT, one of the parameters (</span><span class=DefaultFontHxMailStyle><u>S220</u>) of the generalized model becomes </span><span class=DefaultFontHxMailStyle><u>negative</u>. I’ve tried </span><span class=DefaultFontHxMailStyle><u>not to refine this specific parameter</u> and the pattern is well fitted again. <o:p></o:p></span></p><p class=MsoNormal><span class=DefaultFontHxMailStyle><o:p> </o:p></span></p><p class=MsoNormal><span class=DefaultFontHxMailStyle>My questions are:<o:p></o:p></span></p><ol style='margin-top:0in' start=1 type=I><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'><span class=DefaultFontHxMailStyle>What could be the meaning of the </span><span class=DefaultFontHxMailStyle><u>negative S220 parameter</u>? (note: I have calculated instrument parameters from calibrant and also I’ve investigated the family of 220 planes in the patterns and I didn’t find something weird eg. Bkgr, noise)<o:p></o:p></span></li><li class=MsoListParagraph style='margin-left:0in;mso-list:l0 level1 lfo1'><span class=DefaultFontHxMailStyle>Is it obligatory to refine all the parameters of the generalized model, coming from the selected space group?<o:p></o:p></span></li></ol><p class=MsoListParagraph><span class=DefaultFontHxMailStyle><o:p> </o:p></span></p><p class=MsoNormal><span class=DefaultFontHxMailStyle>Thank you in advance!<o:p></o:p></span></p><p class=MsoNormal><span class=DefaultFontHxMailStyle><o:p> </o:p></span></p><p class=MsoNormal>Best regards,<o:p></o:p></p><p class=MsoNormal>KAITATZI Myrsini<o:p></o:p></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>----------------------------------------------------------<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>PhD Candidate,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Institute of Electronic Structure and Laser (IESL),<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Foundation for Research and Technology - Hellas (FORTH),<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>100 Nikolaou Plastira str, Vassilika Vouton,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>700 13 Heraklion, Crete,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>GREECE<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Office Phone (+30) 2810 391874 <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Lab Phone (+30) 2810 391349<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>Mobile (+30) 6945084322<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'><a href="https://www.iesl.forth.gr/en/research/magnetic-materials"><span style='color:blue'>Quantum Materials & Magnetism Lab</span></a></span><u><span style='color:blue'><o:p></o:p></span></u></p><p class=MsoNormal><span style='font-size:10.0pt;color:black'>----------------------------------------------------------</span><span style='color:black'><o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span class=DefaultFontHxMailStyle><o:p> </o:p></span></p></div></body></html>