<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:10pt">Dear Gavin Abo, Sir,<br><br>In line with the discussion above, I got when I plot E vs c/a the following<br><br><span style="font-weight: bold;">Fit of: E = a1 + a2*x + a3*x^2 + a4*x^3 + a5*x^4<br>a1<span class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> </span></span></span></span>1.000<br></span>a2<span class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> <span class="tab">0.000<span class="tab"> 1.000</span></span></span></span></span></span></span><br>a3<span class="tab"> <span
class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> -0.761 -0.000<span class="tab"> 1.000</span></span></span></span></span></span><br>a4<span class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> <span class="tab"> -0.000<span class="tab"> -0.930<span class="tab"> 0.000<span class="tab"> 1.000</span></span></span></span></span></span></span></span><br>a5</span><span class="tab"><span style="font-weight: bold;"> </span><span class="tab"><span style="font-weight: bold;"> </span><span class="tab"><span style="font-weight: bold;"> </span><span class="tab"><span style="font-weight: bold;"> </span><span
class="tab"><span style="font-weight: bold;"> 0.642</span><span class="tab"><span style="font-weight: bold;"> </span><span class="tab"><span style="font-weight: bold;">0.000<span class="tab"> -0.972<span class="tab"> -0.000<span class="tab"> 1.000</span></span></span> <br></span><br>In this case what should be the value for a2, a3, a4, and a5? <br><br>Thank you in advance for your response.<br>With kind regards<br>Mohammed Lawal <br> </span></span></span></span></span></span></span><div><span><br></span></div><div style="display: block;" class="yahoo_quoted"> <br> <br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 10pt;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12pt;"> <div dir="ltr"> <font face="Arial" size="2"> On
Friday, January 24, 2014 7:08 AM, Gavin Abo <gsabo@crimson.ua.edu> wrote:<br> </font> </div> <div class="y_msg_container"><div id="yiv8953273078"><div>
<div class="yiv8953273078moz-cite-prefix">Below is a summary of previous posts
that should help.<br clear="none">
<br clear="none">
To plot energy vs b/a:<br clear="none">
<br clear="none">
(a) You should be able to rename the scf files and then plot with
the energy vs c/a option of eplot
[<a rel="nofollow" shape="rect" class="yiv8953273078moz-txt-link-freetext" target="_blank" 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 clear="none">
(b) You could also plot energy vs b/a in another program like
Origin
[<a rel="nofollow" shape="rect" class="yiv8953273078moz-txt-link-freetext" target="_blank" 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 clear="none">
<br clear="none">
To get the optimized c/a (or b/a) value, you can calculate it
from the curve fit equation
[<a rel="nofollow" shape="rect" class="yiv8953273078moz-txt-link-freetext" target="_blank" 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 clear="none">
<br clear="none">
An example calculation is given below.<br clear="none">
<br clear="none">
When you plot E vs. c/a with eplot, you should get something like:<br clear="none">
<br clear="none">
Fit of: E = a1 + a2*x + a3*x^2 + a4*x^3 + a5*x^4<br clear="none">
a1 = -2201.24<br clear="none">
a2 = 0.00233422<br clear="none">
a3 = 0.000188276<br clear="none">
a4 = 1.33462e-05<br clear="none">
a5 = 9.76521e-07<br clear="none">
<br clear="none">
From dE/dx = 0, we get the equation:<br clear="none">
<br clear="none">
a2 + 2*a3*x+3*a4*x^2+4*a5*x^3 = 0<br clear="none">
<br clear="none">
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 clear="none">
<br clear="none">
Octave input:<br clear="none">
<br clear="none">
dEdx = [4*9.76521e-07,3*1.33462e-05,2*0.000188276,0.00233422]<br clear="none">
roots(dEdx)<br clear="none">
<br clear="none">
Octave output:<br clear="none">
<br clear="none">
-1.2474 + 8.6889i<br clear="none">
-1.2474 - 8.6889i<br clear="none">
-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 clear="none">
<br clear="none">
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 clear="none">
<br clear="none">
On 1/22/2014 7:22 AM, MAHDI SALMANI HIRMAND wrote:<br clear="none">
</div>
<div class="yiv8953273078yqt2770598339" id="yiv8953273078yqt63325"><blockquote 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></div>
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