[Pw_forum] SCF calculations for molecules in electric fieldsare not converged

[Jibiao Li]

Dear Mostafa,
It happens to be that my research is focused on molecules in ultrahigh electric fields such as 1Ry or higher. The SCF calculations exhibit positive total energies in oscillations. My problem is how to get those calculations converged with your help. Do you or anyone have ideas to resolve this problem?


When I use option of occupations = 'smearing' , the calculations stop and complain that "Error in routine iosys(1): Berry Phase/electric fields only for insulators!". Do you have any ideas to crack this problem? What parameters should I specify?


Thank you very much!


Jibiao Li


&CONTROL
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                      outdir = '/home/jibiao/Calc/molecules/N2/' ,
                  pseudo_dir = '/home/jibiao/Codes/pseudo/' ,
                      prefix = 'N2' ,
                     tstress = .true. ,
                     tprnfor = .true. ,
                    lelfield = .true. ,
 /
 &SYSTEM
                       ibrav = 1,
                   celldm(1) = 15.117815022,
                         nat = 2,
                        ntyp = 1,
                     ecutwfc = 29 ,
                     ecutrho = 180 ,
                 occupations = 'fixed' ,
 /
 &ELECTRONS
            electron_maxstep = 300,
                 mixing_beta = 0.2D0 ,
             diagonalization = 'david' ,
              efield_cart(1) = 1,
              efield_cart(2) = 0,
              efield_cart(3) = 0,
 /
ATOMIC_SPECIES
    N   14.00700  N.pbe-van_ak.UPF
ATOMIC_POSITIONS angstrom
    N      5.122061326    3.999999675    4.000000376    
    N      4.000000000    4.000000000    4.000000000    0  0  0
K_POINTS automatic
  1 1 1   0 0 0






------------------ Original ------------------
From:  "Mostafa Youssef";<mostafa.youssef at aucegypt.edu>;
Date:  Tue, Aug 8, 2017 11:44 PM
To:  "pw_forum"<pw_forum at pwscf.org>; 

Subject:  Re: [Pw_forum] SCF calculations for molecules in electric fieldsare not converged



Dear Jibiao Li,


A field of 1 Ry a.u. is giant and atypical, so one should not be surprised do not converge.  Recall,  1 in Ry a.u.=36.3609*10^10 V/m.


I also noticed that you impose fixed occupations and then apply Gaussian smearing. Those are in contradiction of each other. Apparently the code enforces fixed occupations and ignores the smearing.




Mostafa

AUC, New Cairo, Egypt
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