Graphene absorption spectrum
Posted: Tue Jul 16, 2024 5:03 pm
Dear VASP team,
I am going to compute the absorption spectrum of a graphene-like system. To do so, I started with the GW/BSE approach for an ideal graphene. The PBE starting point provides well-known features, and the PBE-G0W0 level gives qualitatively similar results with wider gaps at the Gamma point, e.g. For your reference, I ran this job using the following INCAR and with/without WAVEDER from PBE_unocc calculations.
System = Gr_GW_PBE
ISMEAR = 0 ; SIGMA = 0.05
ISPIN = 2
IVDW = 11
NBANDS = 672
NELM = 1
ALGO = GW0
NOMEGA = 100
LASPH = .TRUE.
LSPECTRAL = .TRUE.
OMEGAMIN= 0.0100
So far everything looks satisfying. However, solving BSE for these GW results leads to zero strength in the optical transitions given in vasprun.xml for both jobs with/without the WAVEDER file. My INCAR file is as follows and the job report says all gone successfully including the read of WFULL*.tmp files, BSE diagonalizing, and reading the WAVEDER when it is available.
System = Gr_BSE_GW_PBE
ISTART = 1
ISMEAR = 0 ; SIGMA = 0.05
ISPIN = 2
IVDW = 11
NBANDS = 672
NBANDSO = 2; NBANDSV = 12
ALGO = BSE
OMEGAMAX = 60
###CSHIFT = 0.1
What have I misunderstood/missed in this last step?
I use vasp 5.4.4, and since the actual system that I want to study is spin-polarized, I run this test calculation with ISPIN=2 and a small smearing.
Regards,
Masoud
I am going to compute the absorption spectrum of a graphene-like system. To do so, I started with the GW/BSE approach for an ideal graphene. The PBE starting point provides well-known features, and the PBE-G0W0 level gives qualitatively similar results with wider gaps at the Gamma point, e.g. For your reference, I ran this job using the following INCAR and with/without WAVEDER from PBE_unocc calculations.
System = Gr_GW_PBE
ISMEAR = 0 ; SIGMA = 0.05
ISPIN = 2
IVDW = 11
NBANDS = 672
NELM = 1
ALGO = GW0
NOMEGA = 100
LASPH = .TRUE.
LSPECTRAL = .TRUE.
OMEGAMIN= 0.0100
So far everything looks satisfying. However, solving BSE for these GW results leads to zero strength in the optical transitions given in vasprun.xml for both jobs with/without the WAVEDER file. My INCAR file is as follows and the job report says all gone successfully including the read of WFULL*.tmp files, BSE diagonalizing, and reading the WAVEDER when it is available.
System = Gr_BSE_GW_PBE
ISTART = 1
ISMEAR = 0 ; SIGMA = 0.05
ISPIN = 2
IVDW = 11
NBANDS = 672
NBANDSO = 2; NBANDSV = 12
ALGO = BSE
OMEGAMAX = 60
###CSHIFT = 0.1
What have I misunderstood/missed in this last step?
I use vasp 5.4.4, and since the actual system that I want to study is spin-polarized, I run this test calculation with ISPIN=2 and a small smearing.
Regards,
Masoud