<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: times new roman,new york,times,serif; font-size: 12pt; color: #000000'>Thanks a lot. I will try it.<br><br>Chengyang<br><br><hr id="zwchr"><blockquote style="border-left:2px solid rgb(16, 16, 255);margin-left:5px;padding-left:5px;color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From: </b>"Yun Wang" <yun.wang@griffith.edu.au><br><b>To: </b>"PWSCF Forum" <pw_forum@pwscf.org><br><b>Sent: </b>Wednesday, April 24, 2013 3:17:38 PM<br><b>Subject: </b>Re: [Pw_forum] problems of the K points of the unit cell and supercell<br><br><div dir="ltr">Hi Chengyang,<div><br></div><div style=""> You can run a series of calculations with different k-point meshes. The right k-point mesh density can be determined once the total energies converge.</div><div style="">
<br></div><div style="">Cheers,</div><div style="">Yun</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Apr 25, 2013 at 5:18 AM, Chengyang Li <span dir="ltr"><<a href="mailto:li.chengyang@wmich.edu" target="_blank">li.chengyang@wmich.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Dear all<br>
<br>
I have a question about the K points. When I try to repeat the unit cell to get a supercell. I found someone said if the structure is changed, the K points should be changed at the same time if we want to keep the same result. I try to calculate the phonon of the chromium, the atomic positions and cell parameters are like this:<br>
<br>
Unit cell<br>
<br>
ATOMIC_POSITIONS crystal<br>
Cr1 0.000000000 0.000000000 0.000000000<br>
<br>
<br>
CELL_PARAMETERS cubic<br>
0.500000000 0.500000000 0.500000000<br>
-0.500000000 0.500000000 0.500000000<br>
-0.500000000 -0.500000000 0.500000000<br>
<br>
Supercell, there are two unit cells in this cell.<br>
<br>
ATOMIC_POSITIONS crystal<br>
Cr1 0.000000000 0.000000000 0.000000000<br>
Cr1 0.000000000 0.000000000 0.500000000<br>
Cr1 0.500000000 0.500000000 0.250000000<br>
Cr1 0.500000000 0.500000000 0.750000000<br>
<br>
CELL_PARAMETERS<br>
1.000000000 0.000000000 0.000000000<br>
0.000000000 1.000000000 0.000000000<br>
0.000000000 0.000000000 2.000000000<br>
<br>
If I set the unit cell like this<br>
<br>
K_POINTS automatic<br>
4 4 4 1 1 1<br>
<br>
How should I change the k points in the supercell?<br>
<br>
<br>
Thank you for the attention.<br>
<br>
Chengyang Li<br>
<br>
Western Michigan University,<br>
<br>
<br>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><font face="Helv"><font face="Helv">
<p>Dr. Yun Wang<br>Research Fellow<br>Centre for Clean Environment and Energy<br>Griffith School of Environment<br>Gold Coast Campus, Griffith University<br>QLD 4222, Australia<br>Tel:(61-7) 5552 8456<br>Fax:(61-7) 5552 8067</p>
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