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Dear all, <br>
<br>
I think that (using GAO Zhe's notation) both<br>
b (*) c / (|b| |c|)<br>
and <br>
a (*) b / (|a| |b|)<br>
should give the same result, because in the rhombohedral lattice the
three basis vectors form equal angles with each other.<br>
Obviously, a (*) b / (|a (*) b|) is not correct because it would
always give 1 or -1 (and I believe it was just a typo).<br>
<br>
<br>
HTH<br>
<br>
GS<br>
<br>
<br>
On 11/17/2011 06:49 AM, Huiqun Zhou wrote:
<blockquote cite="mid:333916570C304FBE95176B9CEF256B1F@solarflare"
type="cite">
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<div><font face="Arial" size="2">I'm afraid the formula for
calculating cosA should be</font></div>
<div><font face="Arial" size="2">cosA = b (*) c / (|b| | c|)</font></div>
<div> </div>
<div><font face="Arial" size="2">dr. zhou huiqun</font></div>
<div><font face="Arial" size="2">@earth sciences, nanjing
university, china</font></div>
<div> </div>
<blockquote style="border-left: 2px solid rgb(0, 0, 0);
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: none repeat scroll 0%
0% rgb(228, 228, 228);"><b>From:</b> <a
moz-do-not-send="true" title="flux_ray12@163.com"
href="mailto:flux_ray12@163.com">GAO Zhe</a> </div>
<div style="font: 10pt arial;"><b>To:</b> <a
moz-do-not-send="true" title="pw_forum@pwscf.org"
href="mailto:pw_forum@pwscf.org">PWSCF Forum</a> </div>
<div style="font: 10pt arial;"><b>Sent:</b> Wednesday, November
16, 2011 8:53 PM</div>
<div style="font: 10pt arial;"><b>Subject:</b> Re: [Pw_forum]
calculation of lattice parameter and angle of rhombohedral
structure</div>
<div><br>
</div>
<div style="line-height: 1.7; font-family: arial; color: rgb(0,
0, 0); font-size: 14px;">the three basis vectors of
rhombohedral are (after relaxation) :<br>
a = ( 0.636439417 -0.367448469 0.640642896 )<br>
b = ( 0.000000000 0.734896938 0.640642896 )<br>
c = ( -0.636439417 -0.367448469 0.640642896 )<br>
then the lattice paremeter should be: A = sqrt
(a1^2+a2^2+a3^2) * alat = 8.05092296 a.u. .<br>
The angle between two vectors can be calculated by:<br>
cosA = a (*) b / |a (*) b|,<br>
where a and b are basis vectors, (*) represents the dot
product.<br>
<br>
<div>--<br>
GAO Zhe<br>
CMC Lab, MSE, SNU, Seoul, S.Korea<br>
</div>
<br>
At 2011-11-16
20:14:38,"yedu kondalu" <a class="moz-txt-link-rfc2396E" href="mailto:nykondalu@gmail.com"><nykondalu@gmail.com></a> wrote:<br>
<blockquote style="border-left: 1px solid rgb(204, 204, 204);
margin: 0px 0px 0px 0.8ex; padding-left: 1ex;"
id="isReplyContent">Dear users,<br>
<br>
I did the optimization for a compound using variable
cell approximation using PWSCF, which belongs to the space
group R3m(160) Rhombohedral representation. The primitive
vectors in terms of lattice parameter a = 8.25791360 a.u. <br>
a(1) = ( 0.619505 -0.357671 0.698774 )
<br>
a(2) = ( 0.000000 0.715343 0.698774 )
<br>
a(3) = ( -0.619505 -0.357671 0.698774 ) <br>
<br>
after completion of optimization step, the primitive vectors<br>
<br>
CELL_PARAMETERS (alat= 8.25791360)<br>
0.636439417 -0.367448469 0.640642896<br>
0.000000000 0.734896938 0.640642896<br>
-0.636439417 -0.367448469 0.640642896<br>
<br>
can u please explain me <br>
<br>
how can I calculate the lattice parameter <b>a</b> and the
<b>angle (alpha)</b> ???<br>
<br>
Thanks in advance<br>
<br>
Regards<br>
Yedukondalu<br>
</blockquote>
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</blockquote>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Gabriele Sclauzero, EPFL SB ITP CSEA
PH H2 462, Station 3, CH-1015 Lausanne
</pre>
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