[Wien] Ghost band error in SnS2 continued....

[Laurence Marks]

I suggest looking into:

a) Whether experimentally this is a direct or indirect band-gap material.
If it is an indirect gap, what that value is. The number in case.scf2* is
the "minimum gap", not the sometimes larger direct gap. Trust experiment,
do not just follow what someone else did.

b) Look at the DOS to see what the HOMO & LUMO states are, not just the gap.

c) From b), look at what the +U is doing. Is it pushing the d-bands lower,
or the S higher? Use some deep core state as a reference (not simply the
Fermi energy).

d) Try -eece. While it is similar to +U , it is not the same and might work
better.

e) Try forcing the d-states into the core. For this you would use a larger
RMT and instead of -6 use ".985" for your case. This will then use dstart
to handle the tails of the states that are being forced into the core. This
might work, although you will probably need to add a d linearization energy
at something like 1.5 Ryd to avoid getting fake d-states (and ghostbands).
This is somewhat advanced.

On Tue, Jan 28, 2020 at 8:36 AM shamik chakrabarti <shamik15041981 at gmail.com>
wrote:

> I want to simulate Li intercalation voltage in SnS2. But for that I need
> to simulate pristine SnS2 properly....
>
> On Tue, Jan 28, 2020, 19:46 Laurence Marks <laurence.marks at gmail.com>
> wrote:
>
>> Reducing the RMT by 30% is somewhat large.
>>
>> The key question is what are you trying to do? Reproducing a result with
>> Vasp is not good science if that is your purpose. Without that information
>> I doubt that anyone can provide useful advice
>>
>> _____
>> Professor Laurence Marks
>> "Research is to see what everybody else has seen, and to think what
>> nobody else has thought", Albert Szent-Gyorgi
>> www.numis.northwestern.edu
>>
>> On Tue, Jan 28, 2020, 08:11 shamik chakrabarti <shamik15041981 at gmail.com>
>> wrote:
>>
>>>
>>> Dear  Professor Laurence and wien2k users,
>>>
>>>                                       with reference to my earlier mail
>>> on SnS2, I have checked the change in RMT (for avoiding Ghostband) with U
>>> and corresponding band gap. The details are as follows;
>>>
>>> U = 7 eV      RMT reduction 6%     Band gap = 1.460 eV
>>> U = 8 eV      RMT reduction 15%    Band gap= 1.475 eV
>>> U= 9 eV       RMT reduction 30%    Band gap = 1.512 eV
>>>
>>> I have not able to reproduce the band gap ~ 2.1 eV as computed
>>> earlier using Vasp (Phys. Chem. Chem. Phys., 2016, 18, 318). Also,
>>> whether 30% reduction of RMT  is acceptable???
>>>
>>> Looking forward to further guidance from you.
>>>
>>> with regards,
>>>
>>> --
>>> Dr. Shamik Chakrabarti
>>> Research Fellow
>>> Department of Physics
>>> Indian Institute of Technology Patna
>>> Bihta-801103
>>> Patna
>>> Bihar, India
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
Corrosion in 4D: www.numis.northwestern.edu/MURI
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what nobody
else has thought"
Albert Szent-Gyorgi
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