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Dear QE users,<br>
<br>
First of all I thank you all so much for your very useful replies
and advices.<br>
I did again the calculation this time using 16x16x8 k-points with
cold smearing as suggested in PRB 71, 205214 (2005).<br>
I've also increased the precision of the atomic coordinates.<br>
Finally, I preformed the calculation using GGA only, GGA+london, and
LDA.<br>
I got the following results:<br>
<br>
<font color="#000066">GGA GGA -
london
LDA
EXP<br>
<br>
a = 2.46854 angs a = 2.46283 angs
a = 2.44424 a = 2.46067<br>
c = 8.02141 angs c = 6.39949 angs
c = 6.49579 c = 6.705
(6.67 at 0K)<br>
energy = -155.032 energy = -155.146 ev/atom energy
= -155.481 ev/atom</font><br>
<br>
The DFT-D approach improve significatively the length of the c axis.<br>
I'm currently trying to do the same thing with the vdW-DF method
implemented in QE 4.3a but the program crash with the error:<br>
<br>
<i> from ggen : error # 45126<br>
too many g-vectors</i><br>
<br>
Best,<br>
<br>
Eric.<br>
<br>
On 03/23/2011 12:33 PM, Eric Germaneau wrote:
<blockquote cite="mid:4D8A20BE.9020504@gucas.ac.cn" type="cite">
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Dear all,<br>
<br>
I'm trying to optimize unit cell parameter of graphite.<br>
The problem is the c axis gets too long.<br>
Starting from published data my initial parameters are a=4.59203
Bohr and c=12.513 Bohr.<br>
The final values are 4.664 and 15.829 respectively.<br>
I need someone to explain to me what I did wrong, I've attached my
input file.<br>
That's a basic calculation so it's very frustrating to not make it
done.<br>
I thank you in advance,<br>
<br>
Eric.<br>
<br>
<div class="moz-signature">-- <br>
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see in the world<br>
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<a moz-do-not-send="true"
href="mailto:germaneau@gucas.ac.cn">Dr. Éric Germaneau</a><br>
<br>
College of Physical Sciences<br>
Graduate University of Chinese Academy of Sciences<br>
Yuquan Road 19A<br>
Beijing 100049<br>
China<br>
<br>
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<br>
<a href="mailto:germaneau@gucas.ac.cn">Dr. Éric Germaneau</a><br>
<br>
College of Physical Sciences<br>
Graduate University of Chinese Academy of Sciences<br>
Yuquan Road 19A<br>
Beijing 100049<br>
China<br>
<br>
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