Dear Andrea, It would be great if you could share the new epsilon.f90 code. If it takes time to merge it with the develop branch, can you put it in a separate one for now? Best regards, Michal Krompiec Merck KGaA, Darmstadt, Germany
On Wed, 8 Jul 2020 at 20:31, Andrea Ferretti <[email protected]> wrote: > > Dear Anibal, > > you are right, it seems calculation="occ" is documented but no longer > there. As far as I understand, the reason is exactly that it is preferred > to directly compute the quantity of interest and perform convergence > checks on it (epsilon.x should be fast enough, though). > > Regarding the anysotropy: as far as I remember epsilon.x does not > implement symmetries, meaning that kpts need to span the whole BZ. > If you run a scf and a nscf calculation using pw.x and does not pay > attention to this (meaning you have not set nosym=.T. noinv=.T.), kpts > will be symmetrized and only the IBZ wedge will be sampled. In turn this > can lead to spurious anysotropy (besides non-correct results). > > hope it helps > Andrea > > BTW: I have a newer version of epsilon.f90 contributed by Tae-Yun Kim > (Seoul National University, South Korea) which fixes a number of these > issues. Just haven't found the time to include it in the official > distribution. > > > > > The epsilon.x manual (in the PP/DOC folder) shows the possibility of > calculating occupations using the key "occ" within the epsilon.x. It is > > emphasized to be a good tool to analyze convergency against the > broadening parameter and the k points sampling. However, the "occ" > > calculation is not implemented (at least in the version I'm using - > 6.4). Such a calculation was implemented with other packages? > > > > If not, is there a way of verifying the convergence other than > explicitly changing the broadening and k points sampling? > > > > I'm working with an AuAl alloy, trying to evaluate the dielectric > function. Using epsilon.x I've got anisotropic behavior that I was not > > expecting for. Working with pure systems (Au and Al) I concluded that > reducing conv_thr increases the epsilon.x output precision, returning > > the isotropic behavior of the dielectric function. Therefore, to the > alloy (with 12 atoms in the cell), I increased both the conv_thr (1e-13) > > and k points (14 14 14). I still got the anisotropy. Should I go further > (calculations with my actual computing power are becoming very time > > and memory consuming)? > > > > Thanks in advance!! > > > > Anibal Bezerra > > The Federal University of Alfenas > > > > > > -- > Andrea Ferretti, PhD > S3 Center, Istituto Nanoscienze, CNR > via Campi 213/A, 41125, Modena, Italy > Tel: +39 059 2055322; Skype: andrea_ferretti > URL: http://www.nano.cnr.it > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
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