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

[Timrov Iurii]

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> on behalf of Abhirup Patra <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
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