<div dir="ltr"><br> <br><div class="Ih2E3d"><br></div>
<div class="gmail_quote">On Sat, Aug 9, 2008 at 1:52 AM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:giannozz@democritos.it">giannozz@democritos.it</a>></span> wrote:</div><div class="Ih2E3d">> Only for Gamma point phonon one can use "Frozen<br>
> phonon" method because it is much faster.<br>
<br>
</div>not true in general. Each linear-response calculation<br>
costs approx. as much as a self-consistent one, and<br>
you need at least as many scf calculations as<br>
linear-response calculations.<br><br>Dear Sir, <br>I agree with you that for small system each <br>linear-response calculation<br>
costs approx. as much as a self-consistent one, and<br> we need at least as many scf calculations as<br>
linear-response calculations.<br><br>However, IN CASE OF very large system (say about 64 atoms per unit cell), <br>I found that a single representation takes too much computer time <br>compared to a single scf run.<br>
<br>Moreover, in some cluster which have multiple cpu <br>for each node and in some quad or octa core computer, always <br>phonon paralization is much slower than manual <br>scf paralization (I mean manually divide your all scf calculations in <br>
different processors). In case of Frozen phonon method, one can <br>also accomplish the same goal by using less memory and <br>disk space.<br>However, for non-zone center phonon Linear response is the best way. <br>There is still a scope in PWSCF to make Phonon calculation much faster <br>
by implementing the representation number parallization.<br><br>regards,<br>SKS<br>JNCASR<br>BANGALORE <br>
<div class="Ih2E3d"><br><br></div><div class="gmail_quote">On Sat, Aug 9, 2008 at 1:52 AM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:giannozz@democritos.it">giannozz@democritos.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="Ih2E3d"><br>
On Aug 8, 2008, at 18:41 , S. K. S. wrote:<br>
<br>
> Only for Gamma point phonon one can use "Frozen<br>
> phonon" method because it is much faster.<br>
<br>
</div>not true in general. Each linear-response calculation<br>
costs approx. as much as a self-consistent one, and<br>
you need at least as many scf calculations as<br>
linear-response calculations<br>
<div class="Ih2E3d"><br>
Paolo<br>
---<br>
Paolo Giannozzi, Dept of Physics, University of Udine<br>
via delle Scienze 208, 33100 Udine, Italy<br>
Phone +39-0432-558216, fax +39-0432-558222<br>
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