<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><br>Dear Lorenzo,<br><br>Thanks very much for this answer. The informations about the ions system was the must important and I got it.<br><br><br>Thanks once again<br><br><br>*******************************<br>Bertrand SITAMTZE YOUMBI<br>Laboratory of Material Sciences<br>Department of Physics<br>University of Yaounde I-Cameroon<br>***********************************<br>--- En date de : <b>Lun 26.10.09, Lorenzo Paulatto <i><paulatto@sissa.it></i></b> a écrit :<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>De: Lorenzo Paulatto <paulatto@sissa.it><br>Objet: Re: [Pw_forum] System size<br>À: "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Lundi 26 Octobre 2009, 18h20<br><br><div class="plainMail">In data 26 ottobre 2009 alle ore 18:03:00, Bertrand SITAMTZE <br><<a
ymailto="mailto:siyouber@yahoo.fr" href="/mc/compose?to=siyouber@yahoo.fr">siyouber@yahoo.fr</a>> ha scritto:<br>> What is the size of the system in QE calculations (1 unit cell, 2, 3, <br>> ....)?<br><br>Dear Betrand,<br>most of Quantum-ESPRESSO programs and utilities use a plane-wave basis set <br>and periodically boundary conditions: the size of the system is always <br>formally infinite. The ions are repeats infinite times whatever you put in <br>the unit cell.<br><br>The periodicity of electronic wavefunctions is a slightly different story <br>which depends on the number and positions of the k-points. It is a bit <br>long to explain. I can go in details, if necessary (although not tonight <br>for lack of time), but it would be better for you to study it off some <br>solid-state book first and ask for the necessary clarifications.<br><br>best regards<br><br><br>-- <br>Lorenzo
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