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<DIV><FONT face=Arial size=2>Dear Mary,</FONT></DIV>
<DIV><FONT face=Arial size=2>If your structure has a lot of forces you will need
to do MINI first to optimize xyz positions.</FONT></DIV>
<DIV><FONT face=Arial size=2>Also you could check other ground state properties
like cell parameters, c/a, DOS etc. This would give you a clue about any
possible input errors.</FONT></DIV>
<DIV><FONT face=Arial size=2>Hope this helps,</FONT></DIV>
<DIV><FONT face=Arial size=2>Chandrika</FONT></DIV>
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style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=us.white@yahoo.com href="mailto:us.white@yahoo.com">Mary White</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=wien@zeus.theochem.tuwien.ac.at
href="mailto:wien@zeus.theochem.tuwien.ac.at">wien2k</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, August 04, 2007 2:59
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Wien] a serious problem about
optimization of hexagonal cell</DIV>
<DIV><BR></DIV>Dear all users,<BR> Nowadays,I'm
focused on the optimization of hexagonal cell. I know using full-potential
method to optimize the hexagonal or the orthogonal cell is a little trouble.
But I really know how to do this. I have learned the optimization notes in the
web of WIEN2K.I minimized atomic positions and lattice constants as the notes
said. <BR> First, I used the experimental structure on
a high pressure phase to optimize the c/a,for example -4,-2,0,2,4 as the notes
says. Then I plot the E vs c/a.The plot isn't a perfectly parabolic.But the
minimum of energy is still canbe found. So I continue to start a loop over the
five c/a ratios. Five c/a correspond to five different structures,as to every
structure,I optimize the volumes. So, as to every a c/a, I can plot E~V
parabolic,that is,I can get five energy and correspond volumes,these are all
the minimum energy on the parabolic lines.But when I use these datas to get
the EOS,the value of B0 is not coincide with the value got from the
pseudo-potential method.And the finally E~V is a similar line.The range of
pressure got from EOS is very small,almost a same pressure.I am puzzled with
that.<BR> I want to know whether the method and
process I used is right.If something wrong,how I can do ? I am sorry to
waste you so much time. I think the optimization of hexagonal cell is a
generalized problem,so if anyone knows,please give me some advise.Any comments
will be appreciated.Thank you in advance.Thanks a
lot.<BR>
Mary<BR>
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