[QE-users] Electron Phonon Calculation: tolerance limit for P

[mkondrin at hppi.troitsk.ru]

Dear Ramesh, 

Yes, you are right. If you include option la2F=.true. Matdyn.x program will 
calculate lambda file. All examples in tuturial of S. Ponce include this 
option. Resulting lambda file is presented in page 7 of the same tutorial.

Sincerely yours, 
M. Kondrin
On Oct 28 2022, Ramesh Kumar Kamadurai wrote:

> Dear Kondrin Thank you for your suggestion. I actually followed the S 
> Ponce lecture notes from the following link to calculate el-ph coupling 
> constant. 
> https://indico.ictp.it/event/8301/session/96/contribution/534/material/0/0.pdf. 
> But in your message here 
> https://lists.quantum-espresso.org/pipermail/users/2022-September/049463.html 
> you suggest to include la2f = .true for q2r, matdyn.x files as well. 
> After that we should post process the files to get lambda value without 
> using lambda.x. Am I right in understanding your message clearly. ?? 
> Regards K Ramesh Kumar Assistant Professor GITAM, University Vizag, India
>
>
>On Thu, Oct 27, 2022 at 1:53 PM Ramesh Kumar Kamadurai <rkamadur at gitam.edu>
>wrote:
>
>> Dear users I am trying to calculate el-Ph coupling constant and other 
>> properties for a superconductor. The input file is attached. I am a bit 
>> stuck with VC-Relax calculation as the system is not able to stabilize 
>> at 0.0 kbar. I followed all the suggestions given in forum 1. Increased 
>> Cut-off to maximum 2. Tried USPP,NC, Mixed and currently running with 
>> PBE-Sol 3. Sequentially done 2 VC Relax calculation but i am not able to 
>> sort out the issue. &CONTROL
>>     calculation   = "vc-relax"
>>     etot_conv_thr =  4.00000e-05
>>     forc_conv_thr =  1.00000e-04
>>     max_seconds   =  1.72800e+05
>>     nstep         = 100
>>     outdir        = "/home/sjacobs/tmp/"
>>     prefix        = "PDZ-VCRELAX"
>>     pseudo_dir    = "C:\Users\RAMESH\.burai\.pseudopot"
>>     tprnfor       = .TRUE.
>>     tstress       = .TRUE.
>>     verbosity     = "high"
>> /
>>
>> &SYSTEM
>>     a           =  6.36512e+00
>>     degauss     =  7.34986e-03
>>     ecutrho     =  6.40000e+02
>>     ecutwfc     =  8.00000e+01
>>     ibrav       = 2
>>     nat         = 4
>>     nosym       = .FALSE.
>>     nspin       = 1
>>     ntyp        = 3
>>     occupations = "smearing"
>>     smearing    = "marzari-vanderbilt"
>> /
>>
>> &ELECTRONS
>>     conv_thr         =  8.00000e-10
>>     electron_maxstep = 80
>>     mixing_beta      =  4.00000e-01
>>     startingpot      = "atomic"
>>     startingwfc      = "atomic+random"
>> /
>>
>> &IONS
>>     ion_dynamics = "bfgs"
>> /
>>
>> &CELL
>>     cell_dofree    = "all"
>>     cell_dynamics  = "bfgs"
>>     press          =  0.00000e+00
>>     press_conv_thr =  5.00000e-01
>> /
>>
>> K_POINTS {automatic}
>> 12 12 12  0 0 0
>>
>> ATOMIC_SPECIES
>> Ga     69.72300  Ga.pbesol-dnl-rrkjus_psl.1.0.0.UPF
>> Pd    106.42000  Pd_ONCV_PBEsol-1.0.upf
>> Zr     91.22400  zr_pbesol_v1.uspp.F.UPF
>>
>> ATOMIC_POSITIONS {crystal}
>> Zr      0.000000   0.000000   0.000000
>> Ga      0.493162   0.493162   0.493162
>> Pd      0.739743   0.739743   0.739743
>> Pd      0.246581   0.246581   0.246581
>>
>> The output stress is given below
>> entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>>  2.67
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.41
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.82
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>>  0.56
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>>  0.13
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.08
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.23
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.35
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.50
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.63
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.77
>>      entering subroutine stress ...
>>           total   stress  (Ry/bohr**3)                   (kbar)     P=
>> -0.83
>> My question is
>> What is the optimal pressure value to avoid negative frequencies for
>> electron phonon calculation ?
>> Is there any mistake in my input file ?
>> Thanks in advance
>> Regards
>> Ramesh
>> Asst. Professor
>> GITAM University
>> Vizag, India
>>
>>
>