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: [email protected] Phone: +353 899811181, +91 9600752742 On Fri, Feb 14, 2020 at 12:11 PM Timrov Iurii <[email protected]> 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 <[email protected]> on behalf of > Vivek Christhunathan <[email protected]> > *Sent:* Friday, February 14, 2020 12:24:25 PM > *To:* [email protected] > *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: [email protected] > Phone: +353 899811181, +91 9600752742 > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
