Dear Li：<div><br><br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">I am curious about the calculation speed related to "ecutwfc" and "ecutrho". As indicated in the tutorial, ecutwfc represents the energy cutoff (Ry) and ecutrho refers to kinetic energy cutoff for charge density and potential. I cannot fully understand the meaning of that brief description. </blockquote>
<div>If you use Norm-concerving PP, you can just omit the parameter "ecutrho". </div><div>If you use Ultra-soft PP, you must set "ecutrho" as (8~12)X"ecutwfc".</div><div>You will fully understand the "ecutrho" after reading some paper about Ultra-soft PP：） (For example：PRB, 41 7892)</div>
<div><br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">From my experience (vasp), the larger the energy cutoff, the slower the calculation would be, but more accurate. </blockquote>
<div>Yes， it is true for PWscf, too. </div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">I just would like to know how to set the experience values of the two flags for the case of metal bulk (and surface) and metal oxide bulk (and surface)? Thank you.<br clear="all">
</blockquote><div>I think, the value is different with different kind of metal.</div><div>You can take a convergence test to get proper "ecutrho" and "ecutwfc" ：）</div><div> </div><div>____________________________________</div>
</div>Hui Wang<br>School of physics, Nankai University, Tianjin, China<br>
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