[QE-users] Reg- Absorption spectrum using TDDFPT (turbo_davidson.x, turbo_lanczos.x and epsilon.x)
Timrov Iurii
iurii.timrov at epfl.ch
Mon Feb 17 13:24:09 CET 2020
Dear Vivek,
> Can you please provide any useful reference for the Bethe-Salpeter approach to obtain accurate absorption spectra for solids?
You can start from this reference:
G. Onida, L. Reining, A. Rubio, "Electronic excitations: density-functional versus many-body Green's-function approaches", Rev. Mod. Phys. 74, 601 (2002).
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: Monday, February 17, 2020 1:20:21 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] Reg- Absorption spectrum using TDDFPT (turbo_davidson.x, turbo_lanczos.x and epsilon.x)
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<mailto:v.christhunathan1 at nuigalway.ie>
Phone: +353 899811181, +91 9600752742
[https://docs.google.com/uc?export=download&id=1oPtxd7PT5ljQRnuP-Gdf5upjiKPXk7Fz&revid=0B_S3ZLbRRu26NW1YallITFk1ZHMxaStQaUVoMjZ4M2NqcC9BPQ]
On Fri, Feb 14, 2020 at 12:11 PM Timrov Iurii <iurii.timrov at epfl.ch<mailto: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<mailto:users-bounces at lists.quantum-espresso.org>> on behalf of Vivek Christhunathan <vivekppn at gmail.com<mailto:vivekppn at gmail.com>>
Sent: Friday, February 14, 2020 12:24:25 PM
To: users at lists.quantum-espresso.org<mailto: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<mailto:v.christhunathan1 at nuigalway.ie>
Phone: +353 899811181, +91 9600752742
[https://docs.google.com/uc?export=download&id=1oPtxd7PT5ljQRnuP-Gdf5upjiKPXk7Fz&revid=0B_S3ZLbRRu26NW1YallITFk1ZHMxaStQaUVoMjZ4M2NqcC9BPQ]
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