[Wien] spin-orbit (PBE and mBJ) for perovskites

[Tran, Fabien]

These are two different systems: CsPbI3 and CsPbCl3. I suggested to try CsPbCl3 since it works for it. Maybe there is a problem with the values for CsPbI3 in the paper.

________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Peter Blaha <pblaha at theochem.tuwien.ac.at>
Sent: Friday, December 6, 2019 9:07 AM
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] spin-orbit (PBE and mBJ) for perovskites

Note the different lattice parameters in the 2 previously attached
struct files.

Am 05.12.2019 um 22:39 schrieb Tran, Fabien:
> Hi,
>
> Some time ago I did calculations on CsPbCl3 and I could reproduce
> Jishi's results reasonably well except the one in the 1st column("GGA")
> which is probably wrong. I got 0.70 eV (0.71 eV from Jishi) for
> "GGA+SOC", 1.68 eV (1.59 eV from Jishi) for TB-mBJ and 2.86 eV (2.83 eV
> from Jishi) for "present". The only special requirement that was needed
> is a p1/2 LO on Pb. I used RKMAX=9 and de=10 in case.in1. The bug
> reported here
>
> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2019-November/029882.html
>
> is active but has very small effect of 0.01 eV for GGA+SOC. Try CsPbCl3
> instead (struct and inso are attached).
>
> FT
>
> ------------------------------------------------------------------------
> *From:* Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of
> Mikhail Nestoklon <nestoklon at mail.ru>
> *Sent:* Thursday, December 5, 2019 8:21 PM
> *To:* A Mailing list for WIEN2k users
> *Subject:* [Wien] spin-orbit (PBE and mBJ) for perovskites
> Dear wien2k community,
> I plan to do some DFT calculation of inorganic perovskites using WIEN2k
> (19.1 with some patches except the last one for RLO).
> 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.
> What I did:
> Using the file in attachment (I use the lattice constant given in table
> 1 and R_MT indicated in the text) I do
> $ init_lapw -b -vxc 13 -rkmax 9.0 -lvns 6 -fftfac 4 && x kgen (14x14x14)
> && run_lapw -ec 0.00001 -cc 0.0001
> 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.
> 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.
> 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.
> 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.
> The RLO (I tried to add it on Cs, as for Pb it should be useless [1])
> does not help
> 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.
> I did not try to change R_MT: I use the value given in their paper.
> 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?
> Thank you in advance.
> Sincerely yours,
> Mikhail Nestoklon
> [1]
> https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg17828.html
>
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