First of all, the VASP gaps of bulk SnS2 are 1.91 eV, not 2.1 as you are
writing ?????
Then there are other VASP papers, which report different results, in
particular different structural parameters:
(Phys. Chem. Chem. Phys., 2016, 18, 318)
a=3.693 c=11.680 gap: 1.91
https://doi.org/10.1016/j.actamat.2014.03.042:
a = 3.518 Å, c = 5.844 Å), gap 1.92 eV (also PBE+U(9 eV !!
SnS2 is a layered material and all VASP papers used a DFT-D2 (+U)
approach. It could be that your Sn position is quite different from
theirs ???
PS: I would not reduce the RMTs. You will make the effect of U even
smaller with smaller RMTs.
PPS:
I'd use TB-mBJ or hybrid-DFT for band gaps- but you said, band gaps are
not your focus, but the voltage of LiSnO2.
For this you need good structural parameters AND good cohesive energies.
I'd use a vdW-functional (for instance rev-vdW-DF2, see our paper) to
optimize the structure and also the SCAN meta-GGA for the energies (the
formation energy determines the Voltage).
On 1/28/20 3:11 PM, shamik chakrabarti 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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P.Blaha
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