<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">Dear Ashkan Shekaari,<br>
there is no general rule. it depends on how localized the
augmentation charges are.<br>
you should determine this by yourself and do not rely on other
people suggestions.<br>
<br>
how to determine ecutwfc and ecutrho ?<br>
<br>
it's a 2-step procedure:<br>
<br>
1) Run a convergence test assuming the default ecutrho=4*ecutwfc
value: that is just specify ecutwfc in the input and leave
unspecified the ecutrho option. Converge the total energy and
monitor stress and forces as well to make sure you get the
convergence you want.<br>
<br>
This step tells you what is the ecutwfc and ecutrho=4*ecutwfc
for which the variational freedom of wavefuctions AND the
numerical accuracy of augmentation-charge integration are BOTH
sufficient. The latter is usually the harder to get so you should
take this value of ecutrho as the one needed for your system.<br>
<br>
2) Keeping fixed this value of ecutrho you can now test the
convergence w.r.t. ecutwfc and see if you can reduce it without
compromising the convergence of total energy, stress and forces.
This tells you the value of ecutwfc you should use in your system.<br>
<br>
HTH<br>
<br>
stefano<br>
<br>
<br>
stefano<br>
<br>
<br>
<br>
<br>
<br>
stefano<br>
<br>
On 03/06/2016 09:51, ashkan shekaari wrote:<br>
</div>
<blockquote
cite="mid:CAGchC0tabcKHtEq2oXP_wJc_PCFaoVnmmXaSEJSOw_g7QE_W3Q@mail.gmail.com"
type="cite">
<div dir="ltr">Dear experts,
<div><br>
</div>
<div>Is it necessary to take the kinetic energy cut-off for the
charge density and the potential 8-12 times larger than the
energy cut-off for the wave functions for the case of 2D-MoS2?</div>
<div><br>
</div>
<div>Doesn't a less value of about 4 times larger than the
energy cut-off for the wave functions work?</div>
<div><br clear="all">
<div>
<div class="gmail_signature"
data-smartmail="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">
<div><b>--</b></div>
<div><i style="font-size:12.8px">Best,</i></div>
<div><i>Ashkan Shekaari</i></div>
<div><i>Plasma Physics Research
Center</i></div>
<div><i style="font-size:12.8px"><span
style="font-size:12.8px">Science
and Research Branch</span></i></div>
<div><i>I A U, <span
style="font-size:12.8px">14778-93855
Tehran, Iran.</span></i></div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<br>
<pre wrap="">_______________________________________________
Pw_forum mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a>
<a class="moz-txt-link-freetext" href="http://pwscf.org/mailman/listinfo/pw_forum">http://pwscf.org/mailman/listinfo/pw_forum</a></pre>
</blockquote>
<br>
</body>
</html>