Dear Prof. Blaha,<div><br></div><div>Thanks a lot for the answer - from someone originally from the pseudopotential community :-) . I suspected that it was RMT(min) that would define the cutoff, but I had to be sure.</div>
<div><br></div><div>Best regards,</div><div><br></div><div>Marcos<br><br><div class="gmail_quote">On Mon, Jun 6, 2011 at 2:27 PM, Peter Blaha <span dir="ltr"><<a href="mailto:pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im">The energy cutoff for the planewave representation in the interstitial is $E_{max}^{wf}=19$ Ry for the wave functions and $E_{max}^{pot}=196$ Ry for<br>
the potential."<br>
<br></div>
A specification like this comes from the Pseudopotential community. We use different values:<br>
<br>
<br>
The cutoff for the potential (and charge density) is specified in case.in2(c). By default we use GMAX=12, while in this paper<br>
GMAX=14 (E=k^2; 14^2=196 Ry) was used.<br>
<br>
The cutoff for the wave functions is specified in case.in1(c), but as RMT(min) * Kmax<br>
So the knowledge of "19 Ry" cutoff alone is not sufficient. You also need to know what their smallest RMT was.<br>
Then RKmax = RMT(min) * sqrt(19). Eg. an RMT=1.6 (for Oxygens) gives our default RKMax=7<br>
<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="im">
The authors specify their convergence parameters in the following way:<br>
<br>
"Inside the muffin tins wave functions are expanded in spherical harmonics up to $l_{max}^{wf}=10$ and nonspherical contributions to the electron density and potential up to<br>
$l_{max}^{pot}=6$ are used. The energy cutoff for the planewave representation in the interstitial is $E_{max}^{wf}=19$ Ry for the wave functions and $E_{max}^{pot}=196$ Ry for<br>
the potential."<br>
<br></div>
I would like to specify my parameters in the same way. For $l_{max}^{wf}$ and $l_{max}^{pot}$, these parameters are found in <a href="http://case.in" target="_blank">case.in</a> <<a href="http://case.in" target="_blank">http://case.in</a>>:<div class="im">
<br>
<br>
8.00 10 4 (R-MT*K-MAX; MAX L IN WF, V-NMT)<br>
<br>
and the last two would give me $l_{max}^{wf}$ and $l_{max}^{pot}$. However, I am in doubt on how to find the PW cutoff for the wavefunctions in the interstitials and for the<br>
potential (or how to determine these cutoffs, if they can't be readily found in the output files).<br>
<br>
For the wavefunctions, it is somewhat straightforward: kmax^2 gives the cutoff energy in Ry. I suppose I could just take the smallest cutoff (since there will be different kmax<br>
for the different elements) as a specification, or is the maximum/minimum value of kmax used for all elements, instead?<br>
<br>
For the expansion of potentials in plane waves, I'd suppose the energy cutoff would be simply gmax^2 (as specified in case.in2), but I'd like to confirm it, even under the risk of<br>
having made a stupid question :)<br>
<br>
Any help will be greatky appreciated.<br>
<br>
Thanks in advance,<br>
<br>
Marcos<br>
<br>
---------------<br>
Marcos Veríssimo Alves<br>
Universidad de Cantabria, Spain<br>
<br>
<br>
<br></div>
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</blockquote>
<br>
-- <br>
<br>
P.Blaha<br>
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</blockquote></div><br></div>