[QE-users] k-point algorithm is not tested yet turbo davidson

Thu Dec 19 17:48:57 CET 2019

Dear Abhirup,

Thank you for clarifications!

Please note that the turbo_eels code works for the noncollinear spin-polarization (noncolin=.true.), and including the spin-orbit coupling (if needed). The turbo_eels code works for the general k-points implementation (k=0 is allowed), but it does not work for the "gamma_only" case (i.e. using tricks to speed up calculations).

The turbo_lanczos and turbo_davidson codes (which are for the absorption spectroscopy) do not work in the spin-polarized case (both collinear and noncollinear) - yes, you are right.

Best,

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 Abhirup Patra <abhirupp at sas.upenn.edu>
Sent: Thursday, December 19, 2019 5:40:47 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] k-point algorithm is not tested yet turbo davidson

Dear Iurii,

Thanks for the email. Sorry about not explaining it well. Here is what I meant: With spin-polarization and with gamma only kmesh none of the TDDFT code works (i.e. turbo_davidson, turbo_eels, turbo_lanczos). So it is difficult to simulate optical spectra for a "neutral (tot_charge = 0)" doped/defected structure. By "works", I meant that I could run the regular scf-calculation and TDDFT codes for any "non-zero (tot_charge = -1 or +1)" charged structure using "gamma only" kmesh and "non spin-polarization".

Please let me know if it's still confusing.

Best,
Abhirup

-------------------------------------------------------------------------------------------------------------------------------------
Abhirup Patra
Postdoctoral Research Fellow
Department of Chemistry
University of Pennsylvania

On Thu, Dec 19, 2019 at 4:06 AM Timrov Iurii <iurii.timrov at epfl.ch<mailto:iurii.timrov at epfl.ch>> wrote:

Dear Abhirup,

Sorry, I miss the point. Could you clarify please what do you mean by saying "it works"? Do you refer to the k-points implementation of the turbo_davidson code or something else? The k-points algorithm must be disabled for all cases (neutral and charged cases), and if this not the case, then I will modify the code in order to disable it.

Best,

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 Abhirup Patra <abhirupp at sas.upenn.edu<mailto:abhirupp at sas.upenn.edu>>
Sent: Wednesday, December 18, 2019 9:36:51 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] k-point algorithm is not tested yet turbo davidson

Forgot to mention, it only happens if I do not assign any charge to the structure i.e., for neutral case. However, it works for nonzero tot_charge, spin-unpolarized situation with fixed smearing and turb_davidson works fine.

Thanks for your comments.

Best,
Abhirup
-------------------------------------------------------------------------------------------------------------------------------------
Abhirup Patra
Postdoctoral Research Fellow
Department of Chemistry
University of Pennsylvania

On Wed, Dec 18, 2019 at 3:29 PM Abhirup Patra <abhirupp at sas.upenn.edu<mailto:abhirupp at sas.upenn.edu>> wrote:
Thanks, Iurii. Yes, the spectrum with gamma point is quite reasonable but do not match with the experimental observation. It could be some other issue.

However, I am wondering how to do the TDDFT calculation for a doped/defected structure with extra electron or hole. I tried to use turbo_davidson starting from i) scf calculation with npsin= 2 and total magnetization and turbo_davidson does not work since I believe it does not
for spin-polarized system, then, I tried ii) scf calculation without any spin-polarization and the scf calculation did not run since it cannot work with an extra charge and 'fixed' occupation, and, finally, iii) scf with smearing but turbo_davidson does not support scf calculation with smearing (ref: https://lists.quantum-espresso.org/pipermail/users/2017-January/037363.html)

I believe in this case I cannot use TDDFT of QE to calculate absorption spectra of a defected or doped structure. Am I right here?

Best,
Abhirup

-------------------------------------------------------------------------------------------------------------------------------------
Abhirup Patra
Postdoctoral Research Fellow
Department of Chemistry
University of Pennsylvania

On Wed, Dec 18, 2019 at 4:00 AM Timrov Iurii <iurii.timrov at epfl.ch<mailto:iurii.timrov at epfl.ch>> wrote:

Dear Abhirup,

> However, I am not sure with the number of atoms (~120 or more) GW-BSE calculations with supercell is actually feasible.

Yes, I understand the issue. I do not know if it is feasible. You may try to use e.g. Yambo and see how it goes. Otherwise, since you have already quite a big cell, maybe with k=0 you obtain quite a reasonably converged spectrum (to be checked w.r.t. the cell size)  at the TDDFT level in the adiabatic approximation.

Regards,

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 Abhirup Patra <abhirupp at sas.upenn.edu<mailto:abhirupp at sas.upenn.edu>>
Sent: Tuesday, December 17, 2019 4:47:01 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] k-point algorithm is not tested yet turbo davidson

Thanks very much, Iurii. I really appreciate your answer and it does make sense to me. With gamma point only it works fine. And, you are  right, my system is a solid and I am
trying to simulate the optical spectrum. However, I am not sure with the number of atoms (~120 or more) GW-BSE calculations with supercell is actually feasible.

Best,
Abhirup
-------------------------------------------------------------------------------------------------------------------------------------
Abhirup Patra
Postdoctoral Research Fellow
Department of Chemistry
University of Pennsylvania

On Tue, Dec 17, 2019 at 7:50 AM Timrov Iurii <iurii.timrov at epfl.ch<mailto:iurii.timrov at epfl.ch>> wrote:

Dear Abhirup,

As you can see from the error message of the turbo_davidson code, the k-points algorithm is not supported. Only Gamma point sampling can be used.

If I understand correctly, your system is a solid, right? And you want to use a unit cell with a k-points mesh, right? The turbo_davidson cannot be used in this case. You may try to use a supercell with a Gamma point sampling. But be careful when using TDDFT in the adiabatic approximation for the absorption spectroscopy of solids. I recommend that you check literature on this topic. Maybe you will need to resort to the BSE approach.

HTH

Iurii Timrov

--
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 Abhirup Patra <abhirupp at sas.upenn.edu<mailto:abhirupp at sas.upenn.edu>>
Sent: Monday, December 16, 2019 6:12:08 PM
To: Quantum ESPRESSO users Forum
Subject: [QE-users] k-point algorithm is not tested yet turbo davidson

Hello,

I am trying to use turbo_davidson starting from a SCF calculation using PBE without smearing and spin-polarization. This system is a non-metal with bandgap of 2.6 eV. I gave uniform k-mesh as follows for the bcc structure with lattice constant of 10.34 angstrom.

 K_POINTS {crystal_b}
 9
0.0 0.0 0.0 0
0.0 -0.5 0.0 0
0.0 -0.5 0.5 0
0.5 -0.5 0.5 0
0.5 -0.5 0.0 0
0.5 0.0 0.0 0
0.0 0.0 0.0 0
0.0 0.0 0.5 0
0.5 0.0 0.5 0

&lr_input
    prefix = 'pristine_pbe'
    outdir = './'
!    wfcdir = './'
/
&lr_dav
  num_eign = 35,
  num_init = 70,
  num_basis_max = 200,
  start = 0.0d0
  finish = 3.5d0
  step = 0.001d0
  broadening = 0.005d0
/

However, I am getting the following error:

     Error in routine lr_readin (1):
     k-point algorithm is not tested yet

I am wondering if there is a simple way out to this problem other than explicitly testing different k mesh combinations.

Best,
Abhirup
-------------------------------------------------------------------------------------------------------------------------------------
Abhirup Patra
Postdoctoral Research Fellow
Department of Chemistry
University of Pennsylvania
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
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_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
users mailing list users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>
https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso<http://www.max-centre.eu/quantum-espresso>)
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