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Dear All,<BR> <BR>I am trying to vc-relax a supercell made of 60 Carbon atoms. I have realized that during the iterations, the pressure is getting more negative. For example:<BR> <BR>Total Force Pressure (kbar)<BR> <BR>3.042645 -179.66<BR>1.543265 -189.02<BR>0.871984 -193.18 <BR>0.686871 -194.73<BR>0.537735 -195.49<BR>0.421031 -195.96<BR>0.366043 -196.10<BR> <BR> <BR> Is that due to the choice of the pseudopotential, the convergence thresholds or maybe both? I will post a part of the input. Thanks in advance.<BR> <BR> <BR>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>&control</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>prefix='GB mgraphene',</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>calculation='vc-relax',</FONT></SPAN></P>
<P class=ecxMsoPlainText><FONT size=3><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><SPAN> </SPAN></SPAN><SPAN lang=PT-BR style="FONT-FAMILY: 'Courier New'">restart_mode='from_scratch',</SPAN></FONT></P>
<P class=ecxMsoPlainText><SPAN lang=PT-BR style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>pseudo_dir = '/exp/home/caiapo/emoujaes/espresso/espresso-4.1.3/pseudo/',</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=PT-BR style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>outdir='/exp/home/caiapo/emoujaes/espresso/Moujaes-Results/',</FONT></SPAN></P>
<P class=ecxMsoPlainText><FONT size=3><SPAN lang=PT-BR style="FONT-FAMILY: 'Courier New'"><SPAN> </SPAN></SPAN><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'">etot_conv_thr = 1.0D-2,</SPAN></FONT></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>forc_conv_thr = 1.0D-2,</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>tstress = .true.,</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>tprnfor = .true.,<SPAN> </SPAN></FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>/</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>&system<SPAN> </SPAN></FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>ibrav= 0, celldm(1) =1.889725989, nat=60, ntyp= 1, ecutwfc =30.0, ecutrho = 120.D0, occupations='smearing', smearing='mp', degauss=0.01</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>/</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>&electrons</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>conv_thr=1.D-2,<SPAN> </SPAN></FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>mixing_beta=0.7D0,</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>diagonalization='david' </FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>/</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>&ions</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>ion_dynamics = 'bfgs',</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>/</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>&cell</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>cell_dynamics = 'damp-w',</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>/</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3> </FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>CELL_PARAMETERS hexagonal</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>24.52769<SPAN> </SPAN>0.00000<SPAN> </SPAN>0.00000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>0.000003<SPAN> </SPAN>6.614491<SPAN> </SPAN>0.00000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>0.000000<SPAN> </SPAN>0.000000<SPAN> </SPAN>10.0000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3> </FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN></FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>ATOMIC_SPECIES</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>12.0107<SPAN> </SPAN>C.pz-vbc.UPF</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3>ATOMIC_POSITIONS angstrom</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>-11.737980<SPAN> </SPAN>-3.561278<SPAN> </SPAN>0.000000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>-11.057718<SPAN> </SPAN>-1.211571<SPAN> </SPAN>0.000000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>-12.450000<SPAN> </SPAN>-7.189838<SPAN> </SPAN>0.000000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>-12.450000<SPAN> </SPAN>-5.773759<SPAN> </SPAN>0.000000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>-11.329191<SPAN> </SPAN>-4.926800<SPAN> </SPAN>0.000000</FONT></SPAN></P>
<P class=ecxMsoPlainText><SPAN lang=EN-GB style="FONT-FAMILY: 'Courier New'"><FONT size=3><SPAN> </SPAN>C<SPAN> </SPAN>-10.692399<SPAN> </SPAN>-2.603942<SPAN> </SPAN>0.000000</FONT></SPAN></P>
...................<BR> <BR>As you can see I have used a convergence threshold for electrons of the order of 10^-2 (maybe it should be 10^-5??). The convergence on the forces is 10^-2 which I think is fine. the reason for putting such convergence thresholds is to gain a bit of time especially that i do not think one needs to go further down (than 10^-2 forces wise). Maybe also I am using an inconveninet pseudopotential..Any suggestions...<BR> <BR>Elie Moujaes<BR>University of Nottingham<BR>Nottingham<BR>NG7 2RD<BR>UK<BR> <br /><hr />Get a free e-mail account with Hotmail. <a href='http://clk.atdmt.com/UKM/go/197222280/direct/01/' target='_new'>Sign-up now.</a></body>
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