Why would you do a runsp_lapw for a non-magnetic system ???

Spin-orbit is also active for a non-magnetic material.

Don't mix up  spin-polarization with spin-orbit ....

PS: I'm also not sure why you want to include the Pb-5p state as valence ?? I don't think you have to use so small Pb spheres that you get core leakage ?? And with Pb-5p as core you have the full SO-splitting inluded, ....



D.

1. initso_lapw
2. runsp_lapw -so -p -i 40 -ec 0.0001 -cc 0.0001'   Fine ????

I am using both step C and D differently because Dr. Tran suggested for
the same
(http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg03843.html)


One more question:
how iqtlsave will change the calculation if I coose it as "0"?

Kind regards



------------------------------------------------
Dr. K. C. Bhamu
(UGC-Dr. D. S. Kothari Postdoc Fellow)
Department of Physics
Goa University, Goa-403 206
India
Mob. No.  +91-9975238952

On Thu, Nov 10, 2016 at 8:00 PM, Peter Blaha
<pbl...@theochem.tuwien.ac.at <mailto:pbl...@theochem.tuwien.ac.at>> wrote:

    Very good explanation.

    So you should probably use SO + mBJ and see what comes out then ....
    (you should get again a good band gap, although effective masses are
    not necessarily improved by mBJ ...)

    Am 10.11.2016 um 15:24 schrieb John McLeod:

        I have some experience using WIEN2k for metal organic halide
        perovskites.

        PBE without SOC gets the correct band gap for CH3NH3PbI3 (which
        I assume
        is the compound Dr. Bhamu is studying) because of a "fortuitous"
        error
        cancellation between using PBE and ignoring SOC. This is
        reasonably well
        known and has been studied in detail in several manuscripts. SOC+PBE
        results in a significantly underestimated band gap, as one might
        expect.

        I assume Dr. Bhamu is using the calculated low frequency dielectric
        constant (e*), and the calculated effective mass (m*) to
        estimate the
        binding energy using the simple Mott-Wannier model: E_ex =
        m*/e^2 (13.6)
        eV .

        SOC does modify the shape of the bands near the gamma-point (I
        believe
        it reduces the effective mass), and SOC also influences the
        dielectric
        constant. So I think perhaps including SOC and using a scissors
        operation with OPTIC to get the correct band gap may be the most
        straight-forward (if not completely ab initio) method.

        Have you looked at F. Brivio, et al., Phys. Rev. B 89 155204 (DOI:
        10.1103/PhysRevB.89.155204)?
        They go into some detail about different approaches, it may be
        helpful
        for your present situation.

        Regards,
        -John McLeod

        So I do not think SOC can be
        On 2016-11-10 10:02 PM, Peter Blaha wrote:

            I'm not the expert on that topic, but I think you mix up the two
            dielectric constants, which could be a semantic problem. To
            compare
            with a classic experiment, you may need to obtain the ionic
            contribution to the dielectric constant, which as far as I
            know can be
            done using BERRYPI.

            Other comments:
            To obtain the "correct" band gap using PBE is very
            "unusual". For most
            materials (but of course there could be exemptions) the PBE
            band gaps
            should be ~50%  smaller than experiment.

            Pb ??? this is very "relativistic" ! Did you consider spin-orbit
            coupling ?

            And last but not least, I have no idea how you calculate exciton
            binding energies from a single particle spectrum. We would
            do this
            using BSE calculations, but your system is probably too
            complicated
            for this.

            Am 10.11.2016 um 14:26 schrieb Dr. K. C. Bhamu:

                Dear Prof. Peter and Experts
                This is with some more information:

                To put a joint paper on complex Metal-organic halide
                perovskites, I am
                trying to reproduce some experimental results measured by my
                collaborator.

                For my complex system, I got low frequency dielectric
                constant value of
                ~5.6 (at 0.013 eV) and the calculated the exciton
                binding energy  ~0.087
                - 0.095 eV  (85 -97 meV). This is too high because the
                measurements here
                get about 13 meV and a 1-2 transition of ~9.9 meV
                (measured).

                In literature the reported static and optical dielectric
                constants for
                the system are in the range of 17-24 and 4.5-6.5
                respectively using DFT.

                In my case the zero frequency dielectric constant (~
                5.6) is in tune
                with the optical dielectric constants (4.5-6.5).

                I think my value ~5.6 should be in the range of 17-24.
                *Is it so?*
                Please help me to understand it.

                I used PBE functional with 4x4x4 k mesh. I reduced rmt
                by 5% and then
                rmt for Pb and I were reduced by a factor of 0.3. I have
                doubt here??

                 My band gap is in reasonable agreement with the
                experimentally observed
                band gap (1.57eV) +/- 0.1.

                The problem may be that my epsilon value (~5.6) is too
                low and I looked
                up our local measured value of ~18 for the low frequency
                part. If I use
                this value (18) then much better exciton binding
                energies come out.

                What can be an mistake that I may did in calculation? or
                may it be a
                reason of the device fabrication because for
                experimental part some
                p-i-n and n-i-p type device has been framed?


                Kind regards

                Bhamu




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