[QE-users] Reg- Absorption spectrum using TDDFPT (turbo_davidson.x, turbo_lanczos.x and epsilon.x)
Vivek Christhunathan
vivekppn at gmail.com
Mon Feb 17 13:20:21 CET 2020
Dear Iurii,
Many thanks for your prompt reply and for your clear explanation about the
related questions.
I will try my calculation as per your technical comments and I will let you
know here.
Can you please provide any useful reference for the Bethe-Salpeter approach
to obtain accurate absorption spectra for solids?
Kind Regards,
Vivek C
__________________________________
Vivek Christhunathan
PhD researcher
Mechanical Engineering
College of Engineering and Informatics
Room 2053
Alice Perry Engineering Building
National University of Ireland Galway
Ireland
E-mail: v.christhunathan1 at nuigalway.ie
Phone: +353 899811181, +91 9600752742
On Fri, Feb 14, 2020 at 12:11 PM Timrov Iurii <iurii.timrov at epfl.ch> wrote:
> Dear Vivek,
>
>
> In order to obtain accurate absorption spectra for solids, the
> Bethe-Salpeter approach is the right way to go. Nonetheless, please see my
> comments below.
>
>
> epsilon.x is based on DFT and it is the code to compute absorption spectra
> in the independent-particle approximation, while turbo_lanczos.x and
> turbo_davidson.x are based on time-dependent DFT (TDDFT) and include
> interaction effects into account (it is possible to disable interactions
> and obtain the same results as epsilon.x). Moreover, in epsilon.x the
> intensities are not fully correct, because there is a missing term in the
> commutator [V,r] (a contribution from the nonlocal part of the
> pseudo-potential is missing, while in TDDFT codes above it is included).
>
>
> Technical comments: you use a hybrid functional (input_dft = 'pbe0'),
> therefore you should use d0psi_rs = .true. in turbo_lanczos.x and
> turbo_davidson.x in order to have the correct intensities in the
> absorption spectrum (this is true for molecules, while in solids it does
> not help).
>
>
> > ATOMIC_SPECIES
> > Ti 47.867 Ti.upf
> > O 16.00 O.upf
>
>
> Check this page for pseudos:
>
> https://www.materialscloud.org/discover/sssp/table/efficiency
>
>
> Greetings,
>
> Iurii
>
>
> --
> Dr. Iurii Timrov
> Postdoctoral Researcher
> STI - IMX - THEOS and NCCR - MARVEL
> Swiss Federal Institute of Technology Lausanne (EPFL)
> CH-1015 Lausanne, Switzerland
> +41 21 69 34 881
> http://people.epfl.ch/265334
> ------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of
> Vivek Christhunathan <vivekppn at gmail.com>
> *Sent:* Friday, February 14, 2020 12:24:25 PM
> *To:* users at lists.quantum-espresso.org
> *Subject:* [QE-users] Reg- Absorption spectrum using TDDFPT
> (turbo_davidson.x, turbo_lanczos.x and epsilon.x)
>
> Dear QE users,
>
> Greetings!!!
>
> I am trying to find the absorption spectrum for the material 'TiO2'
> supercell (2*1*1) which consists of 24 atoms. I tried a lot to find the
> absorption spectrum by reading all the related threads from QE. I have
> tried with all the methods such as turbo_davidson.x, turbo_lanczos.x and
> epsilon.x. I can only succeed with the use of epsilon.x but I am unable to
> get the same results for the turbo_davidson.x and turbo_lanczos.x. I would
> like to know the reason behind this. And secondly to find an absorption
> spectrum of the material does epsilon.x method gives accurate results when
> compared with the other two?
>
> Thirdly I have tried it for the Zn doped TiO2 supercell. This time all the
> methods did not give a hand for my calculation. The input files are given
> below. I would be very grateful if you help me out in this regard.
>
> Please let me know if you need any further information. Looking forward to
> hearing from you.
>
> Thanks in advance.
>
> # self-consistent calculation
> &control
> calculation = 'scf'
> prefix = 'TiO2'
> pseudo_dir = './'
> outdir = './outTiO2'
> !etot_conv_thr = 1e-5
> forc_conv_thr = 1e-4
> /
> &system
> ibrav = 0
> celldm(1) = 14.113
> nat = 24
> ntyp = 2
> ecutwfc = 80.0
> ecutrho = 800
> nbnd = 300
> input_dft = 'pbe0'
> /
> &electrons
> mixing_beta=0.3
> conv_thr = 1.0d-8
> diagonalization = 'david',
> mixing_mode = 'plain',
> /
> &IONS
> /
> &cell
> /
> CELL_PARAMETERS (alat)
> 1.000927809 0.000000000 0.000000000
> 0.000000000 0.500440909 0.000000000
> 0.000000000 0.000000000 1.235414320
> ATOMIC_SPECIES
> Ti 47.867 Ti.upf
> O 16.00 O.upf
> ATOMIC_POSITIONS (crystal)
> Ti 0.000000000 0.000000000 -0.000006420
> Ti 0.500000000 0.000000000 -0.000006418
> Ti 0.250000017 0.500000000 0.499993602
> Ti 0.750000015 0.500000000 0.499993602
> Ti 0.000000000 0.500000000 0.250006398
> Ti 0.500000000 0.500000000 0.250006394
> Ti 0.250000016 0.000000000 0.750006426
> Ti 0.750000016 0.000000000 0.750006426
> O 0.000000000 0.000000000 0.212511476
> O 0.500000000 0.000000000 0.212511476
> O 0.250000011 0.500000000 0.712511501
> O 0.750000021 0.500000000 0.712511501
> O 0.000000000 0.500000000 0.462514694
> O 0.500000000 0.500000000 0.462514705
> O 0.250000019 0.000000000 0.962514709
> O 0.750000013 0.000000000 0.962514709
> O 0.250000008 0.000000000 0.537488518
> O 0.750000024 0.000000000 0.537488518
> O 0.000000000 0.500000000 0.037488489
> O 0.500000000 0.500000000 0.037488487
> O 0.250000019 0.500000000 0.287485309
> O 0.750000013 0.500000000 0.287485309
> O 0.000000000 0.000000000 0.787485317
> O 0.500000000 0.000000000 0.787485307
> K_POINTS gamma
>
> # turbo_lanczos.x calculation
> &lr_input
> prefix ='TiO2'
> outdir ='./outTiO2'
> !restart_step = 100,
> !restart = .true.
> /
> &lr_control
> itermax = 500
> ipol = 1
> !d0psi_rs = .true.
> /
> # turbo_spectrum.x calculation
> &LR_INPUT
> prefix = 'TiO2'
> outdir = './outTiO2'
> itermax0 = 500
> itermax = 10000
> extrapolation = 'osc'
> epsil = 0.01
> units = 1
> start = 0.0
> end = 4.0
> increment = 0.01
> ipol = 1
> /
> # turbo_davidson.x calculation
> &lr_input
> prefix = 'TiO2'
> outdir = './outTiO2'
> /
> &lr_dav
> !if_dft_spectrum = .false.
> num_eign = 5
> num_init = 10
> num_basis_max = 90
> residue_conv_thr = 1.0E-4
> start = 0.0
> finish = 3.50
> step = 0.001
> broadening = 0.004
> reference = 0.3
> /
> # turbo_spectrum.x calculation
> &lr_input
> prefix = 'TiO2'
> outdir = './outTiO2'
> td = 'davidson'
> epsil = 0.004
> start = 0.0d0
> end = 3.5d0
> increment = 0.001d0
> eign_file = 'TiO2.eigen'
> /
>
> Kind Regards,
>
> Vivek C
>
>
> __________________________________
>
> Vivek Christhunathan
>
> PhD researcher
>
> Mechanical Engineering
>
> College of Engineering and Informatics
>
> Room 2053
>
> Alice Perry Engineering Building
>
> National University of Ireland Galway
>
> Ireland
> E-mail: v.christhunathan1 at nuigalway.ie
> Phone: +353 899811181, +91 9600752742
>
> _______________________________________________
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