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<div class="moz-cite-prefix">Below is a summary of previous posts
that should help.<br>
<br>
To plot energy vs b/a:<br>
<br>
(a) You should be able to rename the scf files and then plot with
the energy vs c/a option of eplot
[<a class="moz-txt-link-freetext" href="http://zeus.theochem.tuwien.ac.at/pipermail/wien/2009-January/012053.html">http://zeus.theochem.tuwien.ac.at/pipermail/wien/2009-January/012053.html</a>].<br>
(b) You could also plot energy vs b/a in another program like
Origin
[<a class="moz-txt-link-freetext" href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08841.html">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08841.html</a>].<br>
<br>
To get the optimized c/a (or b/a) value, you can calculate it
from the curve fit equation
[<a class="moz-txt-link-freetext" href="http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05826.html">http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg05826.html</a>].<br>
<br>
An example calculation is given below.<br>
<br>
When you plot E vs. c/a with eplot, you should get something like:<br>
<br>
Fit of: E = a1 + a2*x + a3*x^2 + a4*x^3 + a5*x^4<br>
a1 = -2201.24<br>
a2 = 0.00233422<br>
a3 = 0.000188276<br>
a4 = 1.33462e-05<br>
a5 = 9.76521e-07<br>
<br>
From dE/dx = 0, we get the equation:<br>
<br>
a2 + 2*a3*x+3*a4*x^2+4*a5*x^3 = 0<br>
<br>
Solving this equation for x, x = -7.7555, which is the optimized
c/a ratio in %. I got x with Octave, but there are other software
programs that you can find on the internet to solve the polynomial
equation.<br>
<br>
Octave input:<br>
<br>
dEdx = [4*9.76521e-07,3*1.33462e-05,2*0.000188276,0.00233422]<br>
roots(dEdx)<br>
<br>
Octave output:<br>
<br>
-1.2474 + 8.6889i<br>
-1.2474 - 8.6889i<br>
-7.7555 + 0.0000i <= This polynomial root is chosen as x,
because the imaginary part is zero and it appears in the energy vs
c/a plot.<br>
<br>
If you also want the minimum E, just plug the x value back into
the curve fit equation and solve for E (= -2201.2495).<br>
<br>
On 1/22/2014 7:22 AM, MAHDI SALMANI HIRMAND wrote:<br>
</div>
<blockquote
cite="mid:1390400558.27502.YahooMailNeo@web120504.mail.ne1.yahoo.com"
type="cite">
<div style="color:#000; background-color:#fff;
font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial,
Lucida Grande, sans-serif;font-size:12pt">
<div>Dear Prof. Blaha,</div>
<div>Please let me know why there is not a program for finding
minimum of c/a or b/a ratio with Wien2k Package when we
optimize c/a or b/a.</div>
<div>eplot program can show curve of Energy Vs. c/a but it
doesn't find minimum of c/a.</div>
<div>Please guide me</div>
<div>With best</div>
<div>Mahdi</div>
</div>
</blockquote>
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