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

Tue Jan 28 17:31:26 CET 2020

I guess that is caused by wrong lattice parameters,
with experimental values of a=3.638 AA and  c=5.88 AA one has already with pure GGA a band gap of 1.4 eV (optical gap about 2 eV)

I wonder why a U of 9 eV should be needed to increase the gap by only 0.6eV (if the indirect gap is 2 eV), seems there is something ill defined.

(Note that there are many experimental values given that are measured under pressure)

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
and
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Laurence Marks [laurence.marks at gmail.com]
Gesendet: Dienstag, 28. Januar 2020 16:45
An: A Mailing list for WIEN2k users
Betreff: Re: [Wien] Ghost band error in SnS2 continued....

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<mailto: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<mailto: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<http://www.numis.northwestern.edu>

On Tue, Jan 28, 2020, 08:11 shamik chakrabarti <shamik15041981 at gmail.com<mailto: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,
[https://ssl.gstatic.com/ui/v1/icons/mail/images/cleardot.gif]

--
Dr. Shamik Chakrabarti
Research Fellow
Department of Physics
Indian Institute of Technology Patna
Bihta-801103
Patna
Bihar, India
_______________________________________________
Wien mailing list
Wien at zeus.theochem.tuwien.ac.at<mailto:Wien at zeus.theochem.tuwien.ac.at>
https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_mailman_listinfo_wien&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=SIzNJ8SCoOK36MOMLf8xb01v7QQ9LleWEu5C-yIOVUs&s=mBm3FBO9lfjzZbqAsqX0bzJJwxtVTbYiarbHKo0zFYM&e=
SEARCH the MAILING-LIST at:  https://urldefense.proofpoint.com/v2/url?u=http-3A__www.mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_index.html&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=SIzNJ8SCoOK36MOMLf8xb01v7QQ9LleWEu5C-yIOVUs&s=PhRj2NuBCcAx1g6I1CXK9bska5vBg7-KKz2aV8DxR6U&e=
_______________________________________________
Wien mailing list
Wien at zeus.theochem.tuwien.ac.at<mailto:Wien at zeus.theochem.tuwien.ac.at>
http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien<https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_mailman_listinfo_wien&d=DwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=pMgcf-lFISfKWN78azpiq4bxRQrEuWAN7bV4gMuckJg&s=A7RL8ZaevZNIlxeUZep8_W-r9QzdRoxWeAh1V5V-Bjk&e=>
SEARCH the MAILING-LIST at:  http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_index.html&d=DwMFaQ&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=pMgcf-lFISfKWN78azpiq4bxRQrEuWAN7bV4gMuckJg&s=2haq4drTXoq0qD9xIAS2EcBreoz5j9l_XHUu4XDro0A&e=>
_______________________________________________
Wien mailing list
Wien at zeus.theochem.tuwien.ac.at<mailto:Wien at zeus.theochem.tuwien.ac.at>
https://urldefense.proofpoint.com/v2/url?u=http-3A__zeus.theochem.tuwien.ac.at_mailman_listinfo_wien&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=pMgcf-lFISfKWN78azpiq4bxRQrEuWAN7bV4gMuckJg&s=A7RL8ZaevZNIlxeUZep8_W-r9QzdRoxWeAh1V5V-Bjk&e=
SEARCH the MAILING-LIST at:  https://urldefense.proofpoint.com/v2/url?u=http-3A__www.mail-2Darchive.com_wien-40zeus.theochem.tuwien.ac.at_index.html&d=DwICAg&c=yHlS04HhBraes5BQ9ueu5zKhE7rtNXt_d012z2PA6ws&r=U_T4PL6jwANfAy4rnxTj8IUxm818jnvqKFdqWLwmqg0&m=pMgcf-lFISfKWN78azpiq4bxRQrEuWAN7bV4gMuckJg&s=2haq4drTXoq0qD9xIAS2EcBreoz5j9l_XHUu4XDro0A&e=

--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu<http://www.numis.northwestern.edu/>
Corrosion in 4D: www.numis.northwestern.edu/MURI<http://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