<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><br><br>--- En date de : <b>Lun 15.2.10, Bertrand SITAMTZE <i><siyouber@yahoo.fr></i></b> a écrit :<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>De: Bertrand SITAMTZE <siyouber@yahoo.fr><br>Objet: Help on ev.x procedures!!!<br>À: "Bertrand SITAMTZE" <siyouber@yahoo.fr><br>Date: Lundi 15 février 2010, 15h19<br><br><div id="yiv1332336319"><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td style="font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-size: inherit; line-height: inherit; font-size-adjust: inherit; font-stretch: inherit; -x-system-font: none;" valign="top"><br>Dear all, I have posted on the forum for ev.x procedures but still waiting for any help in understanding the ev.f90 file.<br><br>please, your help is
welcome.<br><br>*******************************<br>Bertrand SITAMTZE YOUMBI<br>Laboratory of Material Science<br>University of Yaounde I-Cameroon<br>*************************************<br><br><br>--- En date de : <b>Mer 10.2.10, Bertrand SITAMTZE <i><siyouber@yahoo.fr></i></b> a écrit :<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>De: Bertrand SITAMTZE <siyouber@yahoo.fr><br>Objet: Re: [Pw_forum] Fw : ev.x procedures<br>À: "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Mercredi 10 février 2010, 11h38<br><br><div id="yiv484862557"><table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td style="font-family: inherit; font-style: inherit; font-variant: inherit; font-weight: inherit; font-size: inherit; line-height: inherit; font-size-adjust: inherit; font-stretch: inherit;" valign="top"><br>Dear Sandro and all,<br><br>I check the ev.f90 file and the way those
EOS are written do not make it easy to write the analytic form. Please can somebody help in giving the four EOS use in this file?<br><br>Also, the fitting procedure leads to an output file containing a fitting pressure. But the problem I have is that there are negative pressures. What is the unit of the fitting pressure in this file? How to convert it in Pa? Is it correct to have negative pressure?<br><br>Thanks for your answers<br><br>*******************************<br>Bertrand SITAMTZE YOUMBI<br>Laboratory of Material Science<br>University of Yaounde I-Cameroon<br>*************************************<br><br><br><br><br>--- En date de : <b>Jeu 4.2.10, Sandro Scandolo
<i><scandolo@ictp.it></i></b> a écrit :<br><blockquote style="border-left: 2px solid rgb(16, 16, 255); margin-left: 5px; padding-left: 5px;"><br>De: Sandro Scandolo <scandolo@ictp.it><br>Objet: Re: [Pw_forum] Fw : ev.x procedures<br>À: "PWSCF Forum" <pw_forum@pwscf.org><br>Date: Jeudi 4 Février 2010, 0h21<br><br><div class="plainMail">Dear Bernard,<br><br>><br>> So, if I want to plot the P-V diagram, I can just calculate the <br>> pressure for each volume using the EOS,since the fitting parameters <br>> are already known. Is it correct?<br>><br><br>Yes, correct.<br><br>><br>> Also, when implementing the fitting procedure iteratively with ev.x, <br>> on has to choose between the Murnagham, Birch 1 and Birch 2. According <br>> to me, there is nothing in the litterature known as Birch 1 and Birch <br>> 2. I thing they refer to Second order and Third order Birch-Murnagham <br>> EOS. I would like you to
clarify it for me.<br>><br><br>I presume so, but you may wish to check what's inside ev.f90 and let us
<br>know. :-)<br><br>Regards,<br>Sandro<br> <br><br><br>><br>><br>><br>> --- En date de : *Mar 2.2.10, Sandro Scandolo /<<a rel="nofollow">scandolo@ictp.it</a>>/* a <br>> écrit :<br>><br>><br>> De: Sandro Scandolo <<a rel="nofollow">scandolo@ictp.it</a>><br>> Objet: Re: [Pw_forum] Fw : ev.x procedures<br>> À: "PWSCF Forum" <<a rel="nofollow">pw_forum@pwscf.org</a>><br>> Date: Mardi 2 Février 2010, 16h19<br>><br>> Dear Bertrand,<br>><br>> pressure is not an input of your pw calculation. It is an output<br>> of the<br>> ev.x calculation.<br>><br>> What ev.x does is to fit the results of your E(V) pw calculations<br>> to
a<br>> chosen EOS functional form, with a number of parameters. Most<br>> functional<br>> forms (e.g. Birch-Murnaghan) include the parameters K and K' (see<br>> <a rel="nofollow" target="_blank" href="http://en.wikipedia.org/wiki/Birch-Murnaghan_equation_of_state">http://en.wikipedia.org/wiki/Birch-Murnaghan_equation_of_state</a> ).<br>> P(V)<br>> can then be calculated from the chosen E(V) (and the fitted<br>> parameters)<br>> as P(V)=-dE(V)/dV .<br>><br>> Notice that the P(V) calculated form the EOS with the fitted<br>> parameters<br>> may be slightly different with respect to the one calculated by<br>> pw.x at<br>>
the volumes where you did your pw.x calculations. But this is another<br>> story (related to<br>> <a rel="nofollow" target="_blank" href="http://www.quantum-espresso.org/wiki/index.php/Methodological_Background#Stress">http://www.quantum-espresso.org/wiki/index.php/Methodological_Background#Stress</a><br>><br>> ).<br>><br>> So, coming to your question, K' is not obtained by finite<br>> differences,<br>> but rather directly as a result of the E(V) fit.<br>><br>> Sandro<br>><br>><br>> Bertrand SITAMTZE wrote:<br>> ><br>> ><br>> > --- En date de : *Mar 2.2.10, Bertrand SITAMTZE<br>> /<<a
rel="nofollow">siyouber@yahoo.fr</a> </mc/compose?to=<a rel="nofollow">siyouber@yahoo.fr</a>>>/*<br>> > a écrit :<br>> ><br>> ><br>> > De: Bertrand SITAMTZE <<a rel="nofollow">siyouber@yahoo.fr</a><br>> </mc/compose?to=<a rel="nofollow">siyouber@yahoo.fr</a>>><br>> > Objet: ev.x procedures<br>> > À: "pw code" <<a rel="nofollow">pw_forum@pwscf.org</a><br>> </mc/compose?to=<a rel="nofollow">pw_forum@pwscf.org</a>>><br>> > Date: Mardi 2 Février 2010, 11h04<br>> ><br>> > (SORRY, THERE
WAS A SMALL MISTAKE IN MY PREVIOUS MESSAGE)<br>> ><br>> ><br>> > Dear all,<br>> ><br>> > As I know, scf and nscf in pw.x are with zero pressure (please<br>> > correct me if I am
wrong). Thus, when evaluating the EOS<br>> > parameters with ev.x, the code uses the E vs VOLUME data to<br>> > evaluate the bulk modulus throught the second derivative.<br>> But, how<br>> > does the code proceed in order to evaluate the pressure<br>> derivative<br>> > of the bulk modulus K', without varing the pressure? If<br>> otherwise,<br>> > can somebody tell me the range of pressure used to evaluate K'?<br>> ><br>> > Please, note that K' is defined as K'=(dK/dP) at P=0.<br>> ><br>>
><br>> > Thanks very much for your answers.<br>> ><br>> ><br>> ><br>> > ***************************************<br>> > Bertrand SITAMTZE YOUMBI<br>>
> Laboratory of Material Sciences<br>> > University of Yaounde I-Cameroon<br>> > *************************************<br>> ><br>> ><br>> ><br>> ><br>> ------------------------------------------------------------------------<br>> ><br>> > _______________________________________________<br>> > Pw_forum mailing list<br>> > <a rel="nofollow">Pw_forum@pwscf.org</a> </mc/compose?to=<a rel="nofollow">Pw_forum@pwscf.org</a>><br>> > <a rel="nofollow" target="_blank"
href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>> > <br>><br>> -- <br>> Sandro
Scandolo, ICTP | <a rel="nofollow" target="_blank" href="http://www.ictp.it/%7Escandolo">http://www.ictp.it/~scandolo</a><br>> <<a rel="nofollow" target="_blank" href="http://www.ictp.it/%7Escandolo">http://www.ictp.it/%7Escandolo</a>><br>><br>> _______________________________________________<br>> Pw_forum mailing list<br>> <a rel="nofollow">Pw_forum@pwscf.org</a> </mc/compose?to=<a rel="nofollow">Pw_forum@pwscf.org</a>><br>> <a rel="nofollow" target="_blank" href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>><br>><br>> ------------------------------------------------------------------------<br>><br>> _______________________________________________<br>> Pw_forum mailing list<br>> <a
rel="nofollow">Pw_forum@pwscf.org</a><br>> <a rel="nofollow" target="_blank" href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>> <br><br>-- <br>Sandro Scandolo, ICTP | <a rel="nofollow" target="_blank" href="http://www.ictp.it/%7Escandolo">http://www.ictp.it/~scandolo</a><br><br>_______________________________________________<br>Pw_forum mailing list<br><a rel="nofollow">Pw_forum@pwscf.org</a><br><a rel="nofollow" target="_blank" href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</a><br></div></blockquote></td></tr></tbody></table><br>
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