<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Dear Giovanni,<br><br>My coordinates are those taken from 2c position of <br>the crystallographic space group table. I though these correspond to the default (alat) in quantum espresso, <br>in which case mentioning is not mandatory. Isn't it?<br><br>Thanks once more<br><br>--- En date de : <b>Mer 2.9.09, Giovanni Cantele <i><Giovanni.Cantele@na.infn.it></i></b> a écrit :<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>De: Giovanni Cantele <Giovanni.Cantele@na.infn.it><br>Objet: Re: [Pw_forum] Titanium atomic positions<br>À: "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Mercredi 2 Septembre 2009, 16h48<br><br><div class="plainMail">Beside the check of the hcp unit cell, which is crucial, I also guess <br>that you gave the input positions<br>in "crystal" units, didn't you?
If it is the case, I think that you <br>should add the "{ crystal }" string after ATOMIC_POSITIONS. Indeed, the <br>default is "alat" units, I think, namely, cartesian coordinates in <br>celldm(1) units.<br><br>Also do not forget to check the convergence of your results with respect <br>to ecutrho. The default value (4*ecutwfc) must be usually increased (6 <br>to 12 times ecutwfc) if, as in you case, ultrasoft pseudopotentials are <br>used.<br><br>Giovanni<br><br><br>Hande Ustunel wrote:<br>> Dear Bertrand,<br>><br>> Your atomic positions are rather off with a large gap between rumpled Ti<br>> layers. Perhaps you should double-check that your definition of the hcp<br>> unit cell matches that for ibrav=4 in the code. You can find this<br>> information in the Doc directory in your copy of espresso.<br>><br>> Besides, you should be able to check your structure for yourself using<br>> xcrysden (--pwi option). <br>><br>> Best
wishes,<br>> Hande<br>><br>> On Wed, 2 Sep 2009, Bertrand SITAMTZE wrote:<br>><br>> <br>>> Dear all,<br>>><br>>> Titanium belongs to the hexagonal P63/mmc<br>>> (n° 194) space group. I would like somebody to confirm that my attached <br>>> input section concerning the bravais lattice and specially the atomic positions are good.<br>>><br>>> &SYSTEM<br>>> ibrav=4<br>>> celldm(1)=5.576203<br>>> celldm(3)=1.587874<br>>> nat=2<br>>> ntyp=1<br>>> ecutwfc=40.0<br>>> /<br>>> &ELECTRONS<br>>> diagonalization='cg'<br>>> /<br>>> ATOMIC_SPECIES<br>>> Ti 47.867 Ti.pw91-nsp-van.UPF<br>>> ATOMIC_POSITIONS<br>>> Ti 0.3333 0..6666 0.2500<br>>> Ti 0.6666 0.3333 0.7500<br>>> K_POINTS automatic<br>>> 8 8 4 0 0 0<br>>><br>>><br>>>
Best regards<br><br> *********************<br>Bertrand SITAMTZE<br>PhD student<br>Department of Physics<br>University of Yaoundé I-Cameroon<br> ***********************<br><br></div></blockquote></td></tr></table><br>