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<DIV><FONT face=Arial size=2>Dear sir,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thank you. Now, I'm better understanding on this
issue.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>vega</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=Arial
size=2>=================================================================================<BR>Vega
Lew (weijia liu)<BR>PH.D Candidate in Chemical Engineering<BR>State Key
Laboratory of Materials-oriented Chemical Engineering<BR>College of Chemistry
and Chemical Engineering<BR>Nanjing University of Technology, 210009, Nanjing,
Jiangsu, China</FONT></DIV>
<DIV style="FONT: 10pt Tahoma">
<DIV><BR></DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=baroni@sissa.it
href="mailto:baroni@sissa.it">Stefano Baroni</A> </DIV>
<DIV><B>Sent:</B> Saturday, September 13, 2008 8:40 PM</DIV>
<DIV><B>To:</B> <A title=pw_forum@pwscf.org
href="mailto:pw_forum@pwscf.org">PWSCF Forum</A> </DIV>
<DIV><B>Subject:</B> Re: [Pw_forum] Fw: relax is too slow</DIV></DIV></DIV>
<DIV><BR></DIV><BR>
<DIV>
<DIV>On Sep 13, 2008, at 2:20 PM, vega wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
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<DIV><FONT face=Arial size=2>Dear sir,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thank you for your responding.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Could you tell me what is the most important
thing to judge whether the <FONT face="Times New Roman" size=3>accuracy of a
numerical calculation is enough.</FONT></FONT></DIV>
<DIV>The energy? force? atomic coordinates? or any other
things?</DIV></DIV></BLOCKQUOTE>
<DIV><BR></DIV>It depends on what you are interested in, of course. What you are
interested in (geometry, energy, other properties ...) is what you should look
at ... for instance, it is known that obtaining well converged values for the
dielectric constant may require k-point meshes way finer than required for a
plain energy calculation. Here as well as in many other circumstances, the
correct answer is not one that the beginner may like to hear: "it depends"
...</DIV>
<DIV><BR></DIV>
<DIV>life is beatiful and hard. if it were not as hard, it would not be as
beautiful</DIV>
<DIV><BR></DIV>
<DIV>cheers - SB</DIV>
<DIV><BR>
<BLOCKQUOTE type="cite">
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<DIV> </DIV>
<DIV><FONT face=Arial size=2>vega</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>=================================================================================<BR>Vega
Lew (weijia liu)<BR>PH.D Candidate in Chemical Engineering<BR>State Key
Laboratory of Materials-oriented Chemical Engineering<BR>College of Chemistry
and Chemical Engineering<BR>Nanjing University of Technology, 210009, Nanjing,
Jiangsu, China</FONT></DIV>
<DIV style="FONT: 10pt Tahoma">
<DIV><BR></DIV>
<DIV style="BACKGROUND: #f5f5f5">
<DIV style="font-color: black"><B>From:</B> <A title=baroni@sissa.it
href="mailto:baroni@sissa.it">Stefano Baroni</A> </DIV>
<DIV><B>Sent:</B> Saturday, September 13, 2008 6:04 PM</DIV>
<DIV><B>To:</B> <A title=pw_forum@pwscf.org
href="mailto:pw_forum@pwscf.org">PWSCF Forum</A> </DIV>
<DIV><B>Subject:</B> Re: [Pw_forum] Fw: relax is too slow</DIV></DIV></DIV>
<DIV><BR></DIV>the same way as you would choose any other parameter
controlling the accuracy of a numerical calculation. try a value; try a few
others corresponding to increasing accuracy, and stop when you see that the
increase in the accuracy is not worth the extra workload. never forget to use
common sense (whenever it is available).
<DIV><BR></DIV>
<DIV>SB</DIV>
<DIV><BR>
<DIV>
<DIV>On Sep 12, 2008, at 11:36 AM, vega wrote:</DIV><BR
class=Apple-interchange-newline>
<BLOCKQUOTE type="cite">
<DIV>Dear sir<BR>
<BLOCKQUOTE type="cite">vega wrote:<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">As far as I tested, the energy would be within
1% for large supercells,<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite">
<BLOCKQUOTE type="cite">but the coordinates of several atoms may differ
200%.<BR></BLOCKQUOTE></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">doesn't make sense<BR></BLOCKQUOTE><BR>could you
tell me more about how to choose the k point
mesh?<BR><BR>vega<BR>=================================================================================<BR>Vega
Lew (weijia liu)<BR>PH.D Candidate in Chemical Engineering<BR>State Key
Laboratory of Materials-oriented Chemical Engineering<BR>College of
Chemistry and Chemical Engineering<BR>Nanjing University of Technology,
210009, Nanjing, Jiangsu,
China<BR><BR>--------------------------------------------------<BR>From:
"Paolo Giannozzi" <<A
href="mailto:giannozz@democritos.it">giannozz@democritos.it</A>><BR>Sent:
Friday, September 12, 2008 5:27 PM<BR>To: "PWSCF Forum" <<A
href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</A>><BR>Subject: Re:
[Pw_forum] Fw: relax is too slow<BR><BR><BR>
<BLOCKQUOTE type="cite">-- <BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Paolo Giannozzi, Democritos and University of
Udine, Italy<BR></BLOCKQUOTE>
<BLOCKQUOTE
type="cite">_______________________________________________<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite">Pw_forum mailing list<BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><A
href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</A><BR></BLOCKQUOTE>
<BLOCKQUOTE type="cite"><A
href="http://www.democritos.it/mailman/listinfo/pw_forum">http://www.democritos.it/mailman/listinfo/pw_forum</A><BR></BLOCKQUOTE>
<BLOCKQUOTE
type="cite"><BR></BLOCKQUOTE>_______________________________________________<BR>Pw_forum
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<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px">---</SPAN></FONT></DIV>
<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px">Stefano Baroni -
SISSA</SPAN></FONT><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px"> </SPAN></FONT><FONT
class=Apple-style-span size=3><SPAN class=Apple-style-span
style="FONT-SIZE: 12px">&</SPAN></FONT><FONT class=Apple-style-span
size=3><SPAN class=Apple-style-span
style="FONT-SIZE: 12px"> </SPAN></FONT><FONT class=Apple-style-span
size=3><SPAN class=Apple-style-span style="FONT-SIZE: 12px">DEMOCRITOS
National Simulation Center - Trieste</SPAN></FONT></DIV>
<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px"><A
href="http://www.sissa.it/~baroni">http://www.sissa.it/~baroni</A>
/ [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni
(skype)</SPAN></FONT></DIV>
<DIV style="MIN-HEIGHT: 14px; MARGIN: 0px; FONT: 12px Helvetica"><BR
style="FONT-SIZE: 12px"></DIV>
<DIV style="MIN-HEIGHT: 14px; MARGIN: 0px; FONT: 12px Helvetica"><SPAN
class=Apple-style-span style="FONT-SIZE: 14px">
<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px">La morale est une logique de
l'action comme la logique est une morale de la pensée - Jean
Piaget</SPAN></FONT></DIV>
<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span
style="FONT-SIZE: 12px"><BR></SPAN></FONT></DIV></SPAN></DIV>
<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px">Please, if possible,
don't</SPAN></FONT><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px"> </SPAN></FONT><FONT
class=Apple-style-span size=3><SPAN class=Apple-style-span
style="FONT-SIZE: 12px">send me MS Word or PowerPoint
attachments</SPAN></FONT></DIV>
<DIV style="MARGIN: 0px"><FONT class=Apple-style-span size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px">Why? See:</SPAN></FONT><FONT
class=Apple-style-span size=3><SPAN class=Apple-style-span
style="FONT-SIZE: 12px"> </SPAN></FONT><FONT class=Apple-style-span
color=#0023e9 size=3><SPAN class=Apple-style-span style="FONT-SIZE: 12px"><A
href="http://www.gnu.org/philosophy/no-word-attachments.html">http://www.gnu.org/philosophy/no-word-attachments.html</A></SPAN></FONT></DIV>
<DIV><FONT class=Apple-style-span color=#0023e9 size=3><SPAN
class=Apple-style-span style="FONT-SIZE: 12px"><BR
class=webkit-block-placeholder></SPAN></FONT></DIV></DIV></DIV></SPAN><BR
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class=Apple-interchange-newline></DIV></SPAN><BR
class=Apple-interchange-newline></DIV></SPAN><BR
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