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<DIV><FONT size=2 face=Arial>Hi, </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>It's your own responsibility to make clear what
crystal class your system belongs to.</FONT></DIV>
<DIV><FONT size=2 face=Arial>Do you know the symbol of space group of your
system? For your case, if it's Pxxx, </FONT></DIV>
<DIV><FONT size=2 face=Arial>the system </FONT><FONT size=2 face=Arial>should be
simple tetragonal (ibrav=6), if it's Ixxx, it should be base centered
</FONT></DIV>
<DIV><FONT size=2 face=Arial>tetragonal </FONT><FONT size=2
face=Arial>(ibrav=7).</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>zhou huiqun</FONT></DIV>
<DIV><FONT size=2 face=Arial>@earth sciences, nanjing university,
china</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=thisisasafeaccount@gmail.com
href="mailto:thisisasafeaccount@gmail.com">tian kong</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=pw_forum@pwscf.org
href="mailto:pw_forum@pwscf.org">PWSCF Forum</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, June 25, 2011 9:49
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Pw_forum] how to choose
ibrav</DIV>
<DIV><BR></DIV><FONT size=2><FONT face="comic sans ms,sans-serif">yeah, i
think you are right. but what really matters is how to set ibrav in pwscf.
<BR></FONT></FONT><A name=id3900439></A><PRE> ibrav structure celldm(2)-celldm(6)<BR>
<A href="goog_798003211" name=id3900439></A><PRE> 6 Tetragonal P (st) celldm(3)=c/a
7 Tetragonal I (bct) celldm(3)=c/a</PRE><A name=id3900439></A><PRE>simple tetragonal (p)
====================
v1 = a(1,0,0), v2 = a(0,1,0), v3 = a(0,0,c/a)
body centered tetragonal (i)
================================
v1 = (a/2)(1,-1,c/a), v2 = (a/2)(1,1,c/a), v3 = (a/2)(-1,-1,c/a).
<BR>it seems that: if ibrav=6, then A=B≠C. if ibrav=7, then A=B=C.<BR>but what i need is A≠B=C. i don't know if i can choose ibrav=6 or 7, and should i need to change the atoms position after i choose ibrav=6 or 7 ?</PRE>
</PRE><BR clear=all><SPAN
style="FONT-FAMILY: comic sans ms,sans-serif"><U>>>>>>>>>【this
is an email sent by <B><SPAN
style="COLOR: rgb(204,0,0)">tiankong</SPAN></B>】</U></SPAN><BR><BR><BR>
<DIV class=gmail_quote>2011/6/24 GAO Zhe <SPAN dir=ltr><<A
href="mailto:flux_ray12@163.com">flux_ray12@163.com</A>></SPAN><BR>
<BLOCKQUOTE
style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"
class=gmail_quote>In your case, this structure must be simple tetragonal or
body centered tetragonal. Please check your model more carefully from
PDF-card or ICSD database.<BR>P.S.: the choice of ibrav depends on the
knowledge of crystallography, please learn it before you do ab-initio
calculation, since symmetry is a very important and foundamental thing in
this area.<BR><FONT color=#888888>
<DIV>--<BR>GAO Zhe<BR>CMC Lab, MSE, SNU, Seoul, S.Korea<BR></DIV></FONT>
<DIV>
<DIV></DIV>
<DIV class=h5><BR>At 2011-06-24 15:25:10，"tian kong" <<A
href="mailto:thisisasafeaccount@gmail.com"
target=_blank>thisisasafeaccount@gmail.com</A>> wrote:<BR>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(204,204,204) 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex"><FONT
size=2><FONT face="comic sans ms,sans-serif">i have read the help document
about INPUT_PW.htm again and again, but since i'm a newbie, i still don't
know whice one i should choose. can you help me?<BR>here is the
problem:<BR>A=10, B=C=8, cosAB=cosBC=cosAC=0.<BR>can you tell me
ibrav=?<BR>thx a lot !!!<BR clear=all></FONT></FONT><SPAN
style="FONT-FAMILY: comic sans ms,sans-serif"><U>>>>>>>>>【this
is an email sent by <B><SPAN
style="COLOR: rgb(204,0,0)">tiankong</SPAN></B>】</U></SPAN><BR></BLOCKQUOTE><BR><BR><SPAN
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