<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Dear udayagiri,<br><br>Thank very much for this clear answer. I will do it with <br><br>ATOMIC_POSITIONS crystal<br>Ti 0..3333 0.6666 0.2500<br>
Ti 0.6666 0.3333 0.7500<br><br><br>Many thanks once again<br><br>*********************<br>
Bertrand SITAMTZE<br>
PhD student<br>
Department of Physics<br>
University of Yaoundé I-Cameroon<br>
***********************<br><br><br>--- En date de : <b>Mer 2.9.09, udayagiri sai babu <i><udayagiri3@gmail.com></i></b> a écrit :<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>De: udayagiri sai babu <udayagiri3@gmail.com><br>Objet: Re: [Pw_forum] Titanium atomic positions<br>À: Giovanni.Cantele@na.infn.it, "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Mercredi 2 Septembre 2009, 20h52<br><br><div id="yiv1131246991">i am sorry for the previous message which i could not type completely.T his is what i mean<br><br>for the ATOMIC_POSITIONS if you choose "crystal" your lattice coordinates are correct<br>Ti 0.3333 0.6666 0.2500<br>
Ti 0.6666 0.3333 0.7500<br><br>or else you can represent same as <br>ATOMIC_POSITIONS (crystal)<br>
Ti 0 0 0<br>Ti 0.333333 0.666666 0.500000<br>both are same except they are displaced by (1/3,2/3,1/4)<br><br><div class="gmail_quote">On Thu, Sep 3, 2009 at 12:18 AM, udayagiri sai babu <span dir="ltr"><<a rel="nofollow" ymailto="mailto:udayagiri3@gmail.com" target="_blank" href="/mc/compose?to=udayagiri3@gmail.com">udayagiri3@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">for the ATOMIC_POSITIONS if you choose "crystal" your lattice coordinates are correct<div class="im">
<br>Ti 0.3333 0.6666 0.2500<br>Ti 0.6666 0.3333 0.7500<br><br></div>or else you can represent same as <br>ATOMIC_POSITIONS (crystal)<br>
Ti 0 0.2500<div class="im"><br>Ti 0.6666 0.3333 0.7500<br><br></div><div><div></div><div class="h5"><div class="gmail_quote">On Wed, Sep 2, 2009 at 9:28 PM, Giovanni Cantele <span dir="ltr"><<a rel="nofollow" ymailto="mailto:Giovanni.Cantele@na.infn.it" target="_blank" href="/mc/compose?to=Giovanni.Cantele@na.infn.it">Giovanni.Cantele@na.infn.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div>Bertrand SITAMTZE wrote:<br>
> Dear Giovanni,<br>
><br>
> My coordinates are those taken from 2c position of<br>
> the crystallographic space group table. I though these correspond to<br>
> the default (alat) in quantum espresso,<br>
> in which case mentioning is not mandatory.. Isn't it?<br>
><br>
> Thanks once more<br>
><br>
<br>
</div>It is not mandatory to specify the default, but I'm not very sure that<br>
your coordinates are in alat units. From<br>
<a rel="nofollow" target="_blank" href="http://cst-www.nrl.navy.mil/lattice/struk/a3.html">http://cst-www.nrl.navy.mil/lattice/struk/a3.html</a><br>
I understand that (1/3,2/3,1/4) and (2/3,1/3,3/4) are in terms of the<br>
A1, A2 and A3 vectors rather than<br>
the x, y z axes versors. alat positions are cartesian coordinates (in<br>
unit of celldm(1)), which are the same as crystal coordinates only for a<br>
simple cubic lattice.<br>
<br>
If I'm not wrong, as pointed out by someone else, you should check that<br>
the A1, A2, A3 choice shown in the<br>
above link is the same as in Quantum-ESPRESSO (for the latter please<br>
have a look to Doc/INPUT_PW* ). If not, you may specify your own lattice<br>
vectors by using the CELL_PARAMETERS card.<br>
<font color="#888888"><br>
Giovanni<br>
</font><div><div></div><div><br>
<br>
><br>
> --- En date de : *Mer 2.9.09, Giovanni Cantele<br>
> /<<a rel="nofollow" ymailto="mailto:Giovanni.Cantele@na.infn.it" target="_blank" href="/mc/compose?to=Giovanni..Cantele@na.infn.it">Giovanni.Cantele@na.infn.it</a>>/* a écrit :<br>
><br>
><br>
> De: Giovanni Cantele <<a rel="nofollow" ymailto="mailto:Giovanni.Cantele@na.infn.it" target="_blank" href="/mc/compose?to=Giovanni.Cantele@na.infn.it">Giovanni.Cantele@na.infn.it</a>><br>
> Objet: Re: [Pw_forum] Titanium atomic positions<br>
> À: "PWSCF Forum" <<a rel="nofollow" ymailto="mailto:pw_forum@pwscf.org" target="_blank" href="/mc/compose?to=pw_forum@pwscf.org">pw_forum@pwscf.org</a>><br>
> Date: Mercredi 2 Septembre 2009, 16h48<br>
><br>
> 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.<br>
> 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<br>
> respect<br>
> to ecutrho. The default value (4*ecutwfc) must be usually<br>
> increased (6<br>
> to 12 times ecutwfc) if, as in you case, ultrasoft<br>
> 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<br>
> rumpled Ti<br>
> > layers. Perhaps you should double-check that your definition of<br>
> 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<br>
> 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<br>
> attached<br>
> >> input section concerning the bravais lattice and specially the<br>
> 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>
><br>
</div></div>> ------------------------------------------------------------------------<br>
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<br>
</div><div>--<br>
<br>
<br>
<br>
Dr. Giovanni Cantele<br>
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche<br>
Universita' di Napoli "Federico II"<br>
Complesso Universitario di Monte S. Angelo - Ed. 6<br>
Via Cintia, I-80126, Napoli, Italy<br>
Phone: +39 081 676910<br>
Fax: +39 081 676346<br>
E-mail: <a rel="nofollow" ymailto="mailto:giovanni.cantele@cnr.it" target="_blank" href="/mc/compose?to=giovanni.cantele@cnr.it">giovanni.cantele@cnr.it</a><br>
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</div></div></blockquote></div><br><br clear="all"><br></div></div><font color="#888888">-- <br>U.Saibabu<br>PhD student,<br>Deformation mechanisms modeling group,<br>Materials engineering department,<br>IISc Bangalore,<br>
India.<br><br>
</font></blockquote></div><br><br clear="all"><br>-- <br>U.Saibabu<br>PhD student,<br>Deformation mechanisms modeling group,<br>Materials engineering department,<br>IISc Bangalore,<br>India.<br><br>
</div><br></blockquote></td></tr></table><br>