[QE-users] Fermi energy and position of dirac point in 2D electronic band structure
Lorenzo Paulatto
lorenzo.paulatto at cnrs.fr
Wed Jun 22 10:44:50 CEST 2022
Hello Steven,
indeed with a smearing of 0.3eV, it is hard to pinpoint the position of
the Ef with a precision of 0.006eV. You can try using a simpler, more
symmetric, smearing (like Fermi-Dirac), but if it works it would be
mostly by chance. The only definitive solution, is to reduce the
smearing and increase the k-points, or to acknowledge that any
calculation is approximate and live with it.
hth
On 22/06/2022 10:33, Steven Best wrote:
> Hello QE Community,
>
> I have calculated the electronic band structure (without spin orbit
> coupling) of a 2D organometallic topological insulator: triphenyl-Pb,
> reproducing the plot from this paper: Wang, Z., Liu, Z. & Liu, F.
> Organic topological insulators in organometallic lattices.
> Nat Commun 4, 1471 (2013). https://doi.org/10.1038/ncomms2451. I
> obtain very good agreement.
>
> However, I find that for my calculation there is a small mismatch
> between the Fermi energy and the position of the dirac point at K.
> The mismatch is approximately 0.006 eV with the Fermi energy higher.
> I thought this mismatch could be a consequence of the metallic
> smearing used in the calculation.
> The reported contribution to the total energy from the smearing is -TS
> = -0.00570874 Ry = -0.07767136 eV.
> I have used 0.3 eV marzari-vanderbilt smearing in the calculations.
>
> Is this reasoning correct? What other contributions can cause the
> mismatch?
>
> Thanks,
> Steven Best
> PhD Student,
> School of Chemistry and Physics, Queensland University of Technology,
> Brisbane, Australia
>
> Below are my input files (QE version 6.3):
>
> ###########################################################################################################
>
> # pw.x scf calculation
>
> &CONTROL
> calculation = 'scf',
> max_seconds = 72000,
> verbosity = 'high',
> restart_mode = 'from_scratch',
> wf_collect = .T.,
> nstep = 200,
> tstress = .true.,
> tprnfor = .true.,
> outdir = './',
> prefix = 'SCF_triphenyl_Pb_OM_inf_2D_sheet_NONplanar_0.3eV_t304a',
> etot_conv_thr = 1.0d-6,
> forc_conv_thr = 1.0d-5,
> pseudo_dir = './pseudo'
> /
> &SYSTEM
> ibrav = 12,
> A = 12.305661, B = 12.305661, C = 20.0, cosAB = 0.5,
> nat = 32, ntyp = 3, ! C=18, H=12, Pb=2
> ecutwfc = 60.0, ecutrho = 480.0,
> occupations = 'smearing', smearing = 'marzari-vanderbilt', degauss
> = 0.02205,
> /
> &ELECTRONS
> electron_maxstep = 100,
> conv_thr = 1.0d-8,
> mixing_mode = 'plain',
> mixing_beta = 0.4, mixing_ndim = 8,
> diagonalization = 'david'
> /
> &IONS
> ion_dynamics = 'bfgs'
> /
> ATOMIC_SPECIES
> Pb 207.2 Pb.pbe-dn-kjpaw_psl.0.2.2.UPF
> H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF
> C 12.011 C.pbe-n-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS (angstrom)
> C 1.887951458 1.089922558 9.614560235
> C 1.897161739 2.478716980 9.795131247
> C 3.058056895 3.149174969 10.201826686
> C 3.094519107 0.403062014 9.798882538
> C 4.255445582 1.073514486 10.205501492
> C 4.264620685 2.462307471 10.386022641
> C 4.954605459 6.434598051 10.203602904
> C 4.954765288 7.775193715 9.796929960
> C 6.152653343 5.732466782 10.385695674
> C 6.152988872 8.476869452 9.614145680
> C 7.351027374 7.774685777 9.796148892
> C 7.350891338 6.434112052 10.202892391
> C 8.040607478 2.462414124 10.385502375
> C 8.049072424 1.074051311 10.201623729
> C 9.210124709 0.403787071 9.795016930
> C 9.247909382 3.148856515 10.204584582
> C 10.408959312 2.478560082 9.798036472
> C 10.417476033 1.090183030 9.614153988
> H 0.998237207 3.074868116 9.635193425
> H 2.991811789 4.226209592 10.358631992
> H 3.160769651 -0.673988810 9.642207163
> H 3.988739061 5.954004099 10.362184021
> H 3.989028106 8.256228576 9.638913669
> H 5.154406664 0.477394068 10.365382031
> H 7.149446547 0.478191613 10.358631345
> H 8.316631087 5.953081922 10.360913089
> H 8.316906000 8.255223371 9.637391566
> H 9.143302088 -0.672828642 9.635510075
> H 9.314642621 4.225484042 10.364079361
> H 11.308571967 3.074480176 9.641154739
> Pb 0.000000000 0.000000000 8.851674686
> Pb 6.152648942 3.552431083 11.147874419
> K_POINTS (automatic)
> 15 15 1 0 0 0
>
> ###########################################################################################################
>
> # pw.x bands calculation
>
> &CONTROL
> calculation = 'bands',
> max_seconds = 108000,
> verbosity = 'high',
> restart_mode = 'from_scratch',
> wf_collect = .T.,
> nstep = 200,
> tstress = .true.,
> tprnfor = .true.,
> outdir = './',
> prefix = 'SCF_triphenyl_Pb_OM_inf_2D_sheet_NONplanar_0.3eV_t304a',
> etot_conv_thr = 1.0d-6,
> forc_conv_thr = 1.0d-5,
> pseudo_dir = './pseudo'
> /
> &SYSTEM
> ibrav = 12,
> A = 12.305661, B = 12.305661, C = 20.0, cosAB = 0.5,
> nat = 32, ntyp = 3, ! C=18, H=12, Pb=2
> ecutwfc = 60.0, ecutrho = 480.0,
> occupations = 'smearing', smearing = 'marzari-vanderbilt', degauss
> = 0.02205,
> /
> &ELECTRONS
> electron_maxstep = 100,
> conv_thr = 1.0d-8,
> mixing_mode = 'plain',
> mixing_beta = 0.4, mixing_ndim = 8,
> diagonalization = 'david'
> /
> &IONS
> ion_dynamics = 'bfgs'
> /
> ATOMIC_SPECIES
> Pb 207.2 Pb.pbe-dn-kjpaw_psl.0.2.2.UPF
> H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF
> C 12.011 C.pbe-n-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS (angstrom)
> C 1.887951458 1.089922558 9.614560235
> C 1.897161739 2.478716980 9.795131247
> C 3.058056895 3.149174969 10.201826686
> C 3.094519107 0.403062014 9.798882538
> C 4.255445582 1.073514486 10.205501492
> C 4.264620685 2.462307471 10.386022641
> C 4.954605459 6.434598051 10.203602904
> C 4.954765288 7.775193715 9.796929960
> C 6.152653343 5.732466782 10.385695674
> C 6.152988872 8.476869452 9.614145680
> C 7.351027374 7.774685777 9.796148892
> C 7.350891338 6.434112052 10.202892391
> C 8.040607478 2.462414124 10.385502375
> C 8.049072424 1.074051311 10.201623729
> C 9.210124709 0.403787071 9.795016930
> C 9.247909382 3.148856515 10.204584582
> C 10.408959312 2.478560082 9.798036472
> C 10.417476033 1.090183030 9.614153988
> H 0.998237207 3.074868116 9.635193425
> H 2.991811789 4.226209592 10.358631992
> H 3.160769651 -0.673988810 9.642207163
> H 3.988739061 5.954004099 10.362184021
> H 3.989028106 8.256228576 9.638913669
> H 5.154406664 0.477394068 10.365382031
> H 7.149446547 0.478191613 10.358631345
> H 8.316631087 5.953081922 10.360913089
> H 8.316906000 8.255223371 9.637391566
> H 9.143302088 -0.672828642 9.635510075
> H 9.314642621 4.225484042 10.364079361
> H 11.308571967 3.074480176 9.641154739
> Pb 0.000000000 0.000000000 8.851674686
> Pb 6.152648942 3.552431083 11.147874419
> K_POINTS (crystal_b)
> 4
> 0.0 0.0 0.0 30 ! Gamma
> 0.666666667 0.333333333 0.0 30 ! K
> 0.5 0.5 0.0 30 ! M
> 0.0 0.0 0.0 30 ! Gamma
>
> ###########################################################################################################
>
> # post-processing bands.x
>
> &bands
> outdir = './'
> prefix = 'SCF_triphenyl_Pb_OM_inf_2D_sheet_NONplanar_0.3eV_t304a',
> filband =
> 't304c_triphenyl_Pb_OM_inf_2D_sheet_NONp_0.3eV_kpath1.bands.dat',
> lsym = .true.
> /
>
> ###########################################################################################################
>
>
>
>
> _______________________________________________
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing listusers at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
--
Dr. Lorenzo Paulatto
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université
phone: +33 (0)1 442 79822 / skype: paulatz
http://www.impmc.upmc.fr/~paulatto/ - https://anharmonic.github.io/
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20220622/92ca2fbe/attachment.html>
More information about the users
mailing list