<html><head></head><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_1446561340979_2755" dir="ltr">is this Okay or I should take an action?</div><div id="yui_3_16_0_1_1446561340979_2755" dir="ltr"><br></div><div id="yui_3_16_0_1_1446561340979_2755" dir="ltr"><br></div> <br><div class="qtdSeparateBR"><br><br></div><div class="yahoo_quoted" style="display: block;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;"> <div dir="ltr"> <font size="2" face="Arial"> On Tuesday, November 3, 2015 4:26 AM, Nicola Marzari <nicola.marzari@epfl.ch> wrote:<br> </font> </div> <br><br> <div class="y_msg_container">On 03/11/2015 10:13, Jaret Qi wrote:<br clear="none">> Dear QE users,<br clear="none">> Why total forces are different in the last relaxation step and the final<br clear="none">> step that pw.x performs once the criteria satisfies, does this mean<br clear="none">> relaxation not good?<br clear="none">> take a look :<br clear="none"><br clear="none">Hi - the code tells you exactly what has happened:<div class="yqt2749629250" id="yqtfd44639"><br clear="none"><br clear="none">> A final scf calculation at the relaxed structure.<br clear="none">> The G-vectors are recalculated for the final unit cell<br clear="none">> Results may differ from those at the preceding step.</div><br clear="none"><br clear="none"><br clear="none">This happens because different unit cells at the same cutoff have different<br clear="none">seta of corresponding plane waves - for an explanation you could check<br clear="none">G Francis and MC Payne circa 1991 (JPCondMatt) or G-M Rignanese<br clear="none">et al PRB circa 1996.<br clear="none"><br clear="none"> nicola<br clear="none"><br clear="none">-- <br clear="none">----------------------------------------------------------------------<br clear="none">Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL<br clear="none">Director, National Centre for Competence in Research NCCR MARVEL, EPFL<br clear="none"><a shape="rect" href="http://theossrv1.epfl.ch/Main/Contact" target="_blank">http://theossrv1.epfl.ch/Main/Contact </a><a shape="rect" href="http://nccr-marvel.ch/en/project" target="_blank">http://nccr-marvel.ch/en/project</a><div class="yqt2749629250" id="yqtfd58405"><br clear="none"></div><br><br></div> </div> </div> </div></div></body></html>