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 the potential."
A specification like this comes from the Pseudopotential community. We use different values: The cutoff for the potential (and charge density) is specified in case.in2(c). By default we use GMAX=12, while in this paper GMAX=14 (E=k^2; 14^2=196 Ry) was used. The cutoff for the wave functions is specified in case.in1(c), but as RMT(min) * Kmax So the knowledge of "19 Ry" cutoff alone is not sufficient. You also need to know what their smallest RMT was. Then RKmax = RMT(min) * sqrt(19). Eg. an RMT=1.6 (for Oxygens) gives our default RKMax=7 > The authors specify their convergence parameters in the following way: > > "Inside the muf?n 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 > $l_{max}^{pot}=6$ 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 > the potential." > > I would like to specify my parameters in the same way. For $l_{max}^{wf}$ and > $l_{max}^{pot}$, these parameters are found in case.in <http://case.in>: > > 8.00 10 4 (R-MT*K-MAX; MAX L IN WF, V-NMT) > > 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 > potential (or how to determine these cutoffs, if they can't be readily found > in the output files). > > 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 > for the different elements) as a specification, or is the maximum/minimum > value of kmax used for all elements, instead? > > 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 > having made a stupid question :) > > Any help will be greatky appreciated. > > Thanks in advance, > > Marcos > > --------------- > Marcos Ver?ssimo Alves > Universidad de Cantabria, Spain > > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- P.Blaha -------------------------------------------------------------------------- Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna Phone: +43-1-58801-15671 FAX: +43-1-58801-15698 Email: blaha at theochem.tuwien.ac.at WWW: http://info.tuwien.ac.at/theochem/ --------------------------------------------------------------------------