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<div>Thank you.</div>
<div>Recently I tried to check also PbSe and there I saw this problem. With RLOs when I go above de=8 the total energy starts to increase and SO also behaves strangely. I understood that there is a problem with RLO and tried to do the calculations without RLO. From your answers I conclude that it was a bad decision, RLO are needed, but «de» should be limited.</div>
<div>And what indicates that I need RLOs for the cases where it is not completely straightforward? Should I try to check the figure like the Fig1 in Kuneš et al [PRB, 64, 153102 (2001)], and if I see similar behavior, then I definitely need RLO? Or just «6p elements beginning with Hg and actinides» as mentioned in Singh and Nordstrom book?</div>
<div> </div>
<div>Sincerely yours,</div>
<div>Mikhail Nestoklon</div>
<div> </div>
<div> </div>
<blockquote style="border-left:1px solid #0857A6; margin:10px; padding:0 0 0 10px;">Вторник, 10 декабря 2019, 10:46 +03:00 от Peter Blaha <pblaha@theochem.tuwien.ac.at>:<br>
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<div id="style_15759639932019893505_BODY">Don't go above EMAX=10 for SO calculations with RLOs.<br>
<br>
On 12/9/19 9:32 PM, Mikhail Nestoklon wrote:<br>
> Dear Prof. Blaha,<br>
> Thank you for clarification. I think, now I more or less understand what<br>
> is happening.<br>
> It seems, this issue is very easy to miss. Do you have any practical<br>
> recommendation how to spot this kind of problem in the calculations of<br>
> non-trivial material with few atoms?<br>
> Sincerely yours,<br>
> Mikhail Nestoklon<br>
><br>
> Понедельник, 9 декабря 2019, 19:02 +03:00 от Peter Blaha<br>
> <<a href="/compose?To=pblaha@theochem.tuwien.ac.at">pblaha@theochem.tuwien.ac.at</a>>:<br>
> Hi,<br>
><br>
> Fist of all: The RLOs (p-1/2)-LOs were originally designed to improve<br>
> the SO splitting of semicore states. There it makes a big difference and<br>
> is essential to converge E-tot in a meaningful way.<br>
><br>
> (By meaningful I do not mean the absolute number as you tested it, but<br>
> an E-tot difference of 2 calculations at eg. 2 volumes).<br>
><br>
> This can be best seen if you compare these semicore eigenvalues with the<br>
> eigenvalues of case.outputst, where the fully-relativistic splitting can<br>
> be found and compared.<br>
><br>
> You can also add it in a case like Pb (usually, Pb does not have<br>
> semicore p-states), but the effect MUST be small.<br>
><br>
> Most importantly, you MUST NOT have a too large E-max, because when the<br>
> spurious LO-eigenvalues of the APW+lo method enter in the spectrum at<br>
> high energy, you may get a problem as indicated below:<br>
><br>
> I checked this for a free Pb-atom (in a big box).<br>
><br>
> lapwso with Emax=10 gives:<br>
><br>
> -1.5996189 -1.5996189 -1.5996189 -1.5996189 -1.4111046<br>
> -1.4111046 -1.4111046 -1.4111046 -1.4110328 -1.4110328<br>
> -0.8489490 -0.8489490 -0.3028265 -0.3028265 -0.2040009<br>
> -0.2040009 -0.2040009 -0.2040009 -0.0106114 -0.0106114<br>
><br>
> while with EMAX=15 I get 6 spurious ghostbands ("bad Pb-5p states):<br>
> -8.2276000 -8.2276000 -3.1336676 -3.1336676 -3.1336591<br>
> -3.1336591 -1.6001880 -1.6001880 -1.6001880 -1.6001880<br>
> -1.4113465 -1.4113465 -1.4113464 -1.4113464 -1.4112735<br>
> -1.4112735 -0.8489490 -0.8489490 -0.2886641 -0.2886641<br>
> -0.2000960 -0.2000960 -0.2000960 -0.2000960 -0.0106114<br>
><br>
> The SO-splitting of 6p states in the Pb atom is 0.109 Ry, while the<br>
> "good" lapwso calculations yield 0.099, but the "bad ones only 0.088<br>
> Without the RLO the SO splitting is 0.092, so still better than the<br>
> "bad" calculation.<br>
><br>
> Eventually one can avoid this switching back to LAPW for the Pb-p<br>
> states.<br>
><br>
> Peter Blaha<br>
><br>
> On 12/9/19 3:30 PM, Mikhail Nestoklon wrote:<br>
> > Dear Dr. Tran,<br>
> > Thank you for the suggestion. Indeed, for CsPbCl3 I get very similar<br>
> > values (0.70 for PBE-SO and 1.67eV for TB-mBJ) and if I add RLO on Pb<br>
> > for CsPbI3 at least for PBE-SO I have something close to value<br>
> given in<br>
> > Jishi.<br>
> > However, now I have a general question. How to understand that I<br>
> need to<br>
> > add RLO in this situation? Should I just try to add RLO on heavy<br>
> atoms<br>
> > and if the result changes prefer the values given by +RLO<br>
> calculations?<br>
> > Or I had to suspect that I need to add RLO when realized that the<br>
> result<br>
> > does not converge until de>15?<br>
> > Sincerely yours,<br>
> > Mikhail Nestoklon<br>
> ><br>
> > Пятница, 6 декабря 2019, 0:39 +03:00 от "Tran, Fabien"<br>
> > <<a href="/compose?To=fabien.tran@tuwien.ac.at">fabien.tran@tuwien.ac.at</a> </compose?To=fabien.tran@tuwien.ac.at><br>
> </compose?To=fabien.tran@tuwien.ac.at>>:<br>
> ><br>
> > Hi,<br>
> ><br>
> > Some time ago I did calculations on CsPbCl3 and I could reproduce<br>
> > Jishi's results reasonably well except the one in the 1st<br>
> > column("GGA") which is probably wrong. I got 0.70 eV (0.71 eV from<br>
> > Jishi) for "GGA+SOC", 1.68 eV (1.59 eV from Jishi) for TB-mBJ and<br>
> > 2.86 eV (2.83 eV from Jishi) for "present". The only special<br>
> > requirement that was needed is a p1/2 LO on Pb. I used RKMAX=9 and<br>
> > de=10 in case.in1. The bug reported here<br>
> ><br>
> ><br>
> <a href="http://zeus.theochem.tuwien.ac.at/pipermail/wien/2019-November/029882.html" target="_blank">http://zeus.theochem.tuwien.ac.at/pipermail/wien/2019-November/029882.html</a><br>
> ><br>
> > is active but has very small effect of 0.01 eV for GGA+SOC. Try<br>
> > CsPbCl3 instead (struct and inso are attached).<br>
> ><br>
> > FT<br>
> ><br>
> ><br>
> ------------------------------------------------------------------------<br>
> > *From:* Wien <<a href="/compose?To=wien%2dbounces@zeus.theochem.tuwien.ac.at">wien-bounces@zeus.theochem.tuwien.ac.at</a><br>
> </compose?To=wien%2dbounces@zeus.theochem.tuwien.ac.at>> on behalf of<br>
> > Mikhail Nestoklon <<a href="/compose?To=nestoklon@mail.ru">nestoklon@mail.ru</a> </compose?To=nestoklon@mail.ru>><br>
> > *Sent:* Thursday, December 5, 2019 8:21 PM<br>
> > *To:* A Mailing list for WIEN2k users<br>
> > *Subject:* [Wien] spin-orbit (PBE and mBJ) for perovskites<br>
> > Dear wien2k community,<br>
> > I plan to do some DFT calculation of inorganic perovskites using<br>
> > WIEN2k (19.1 with some patches except the last one for RLO).<br>
> > I’ve started from attempt to reproduce the values from Jishi et al.,<br>
> > JPCC 118, 28344 (2014), but can not get the numbers given in Table 2<br>
> > even for cubic CsPbI_3. The difference seem to stem from the<br>
> spin-orbit.<br>
> > What I did:<br>
> > Using the file in attachment (I use the lattice constant given in<br>
> > table 1 and R_MT indicated in the text) I do<br>
> > $ init_lapw -b -vxc 13 -rkmax 9.0 -lvns 6 -fftfac 4 && x kgen<br>
> > (14x14x14) && run_lapw -ec 0.00001 -cc 0.0001<br>
> > I use -lvns 6, the difference with the result using standard value<br>
> > is small, in Jishi et al. it is mentioned that l_{max}=10 which is<br>
> > default, assuming they might have meant lvns I tried lvns=10, the<br>
> > difference with lvns=6 is close to zero. I also tried to put Pb p3/2<br>
> > orbitals to core (if I put P1/2 to valence the result is strange,<br>
> > but this is a separate question) and see no difference.<br>
> > For k-mesh I check the convergence and see that for 14x14x14 the<br>
> > total energy convergence is below 1mRy and GAP is below 1 meV which<br>
> > is fine, so I am using this k mesh.<br>
> > Then I check the RKMAX convergence. For Rmt*Kmax =9 without<br>
> > spin-orbit I get the same number as in Table 2, but I see that this<br>
> > number is not fully converged: if I increase RKMAX further the total<br>
> > energy decreases for 8mRy and gap increases for almost 6 meV. I find<br>
> > it acceptable to use RKMAX=12: only then it is <1mRy and ~1meV for<br>
> > total energy and gap respectively. The gap with these numbers is<br>
> > 1.329meV which is 5 meV different from Table 2, this difference is<br>
> > probably acceptable.<br>
> > However, when I switch on the spin-orbit, the difference is huge.<br>
> > With the default values (I only increase llmax, however it does not<br>
> > change much) I get GAP about 0.269meV, which is almost 4 times<br>
> > different from the value given in Jishi et al. Table 2. As the SO<br>
> > value depends on de (in case.in1), I increase this parameter and<br>
> > check the value of GAP and also spin-orbit splitting of conduction<br>
> > and valence band (difference between energies of Gamma_8 and Gamma_7<br>
> > in R point). GAP and spin-orbit in conduction band fully (below<br>
> > 1meV) converge only when de=15. Still, the band gap is 0.259eV which<br>
> > is too far from value given in Jishi et al.<br>
> > The RLO (I tried to add it on Cs, as for Pb it should be useless<br>
> > [1]) does not help<br>
> > With the same parameters I do the mBJ run (TB-mBJ). As expected, the<br>
> > gap increases, but up to 0.722 eV which is two times different from<br>
> > the value given in Jishi et al.<br>
> > I did not try to change R_MT: I use the value given in their paper.<br>
> > The fact that I do reproduce the number given for PBE without<br>
> > spin-orbit indicates that I hardly did any mistake in the structure.<br>
> > However, the difference in the numbers with spin-orbit is too large<br>
> > to be explained by unconverged results, both on my and their side.<br>
> > Could you help me to understand, how can I reproduce their results?<br>
> > Thank you in advance.<br>
> > Sincerely yours,<br>
> > Mikhail Nestoklon<br>
> > [1]<br>
> ><br>
> <a href="https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17828.html" target="_blank">https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17828.html</a><br>
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> --<br>
><br>
> P.Blaha<br>
> --------------------------------------------------------------------------<br>
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna<br>
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