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<div>Dear wien2k community,<br>
I plan to do some DFT calculation of inorganic perovskites using WIEN2k (19.1 with some patches except the last one for RLO).</div>
<div>I’ve started from attempt to reproduce the values from Jishi et al., JPCC 118, 28344 (2014), but can not get the numbers given in Table 2 even for cubic CsPbI_3. The difference seem to stem from the spin-orbit.</div>
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<div>What I did:</div>
<div>Using the file in attachment (I use the lattice constant given in 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 (14x14x14) && run_lapw -ec 0.00001 -cc 0.0001</div>
<div>I use -lvns 6, the difference with the result using standard value is small, in Jishi et al. it is mentioned that l_{max}=10 which is default, assuming they might have meant lvns I tried lvns=10, the difference with lvns=6 is close to zero. I also tried to put Pb p3/2 orbitals to core (if I put P1/2 to valence the result is strange, but this is a separate question) and see no difference.</div>
<div>For k-mesh I check the convergence and see that for 14x14x14 the total energy convergence is below 1mRy and GAP is below 1 meV which is fine, so I am using this k mesh. </div>
<div>Then I check the RKMAX convergence. For Rmt*Kmax =9 without spin-orbit I get the same number as in Table 2, but I see that this number is not fully converged: if I increase RKMAX further the total energy decreases for 8mRy and gap increases for almost 6 meV. I find it acceptable to use RKMAX=12: only then it is <1mRy and ~1meV for total energy and gap respectively. The gap with these numbers is 1.329meV which is 5 meV different from Table 2, this difference is probably acceptable.</div>
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<div>However, when I switch on the spin-orbit, the difference is huge. With the default values (I only increase llmax, however it does not change much) I get GAP about 0.269meV, which is almost 4 times different from the value given in Jishi et al. Table 2. As the SO value depends on de (in case.in1), I increase this parameter and check the value of GAP and also spin-orbit splitting of conduction and valence band (difference between energies of Gamma_8 and Gamma_7 in R point). GAP and spin-orbit in conduction band fully (below 1meV) converge only when de=15. Still, the band gap is 0.259eV which is too far from value given in Jishi et al.</div>
<div>The RLO (I tried to add it on Cs, as for Pb it should be useless [1]) does not help</div>
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<div>With the same parameters I do the mBJ run (TB-mBJ). As expected, the gap increases, but up to 0.722 eV which is two times different from the value given in Jishi et al.</div>
<div>I did not try to change R_MT: I use the value given in their paper.</div>
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<div>The fact that I do reproduce the number given for PBE without spin-orbit indicates that I hardly did any mistake in the structure. However, the difference in the numbers with spin-orbit is too large to be explained by unconverged results, both on my and their side. Could you help me to understand, how can I reproduce their results?</div>
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<div>Thank you in advance.</div>
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<div>Sincerely yours,<br>
Mikhail Nestoklon</div>
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<div>[1] https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17828.html</div>
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