[Pw_forum] about relax in electric field

[Q.J.Wang]

Dear all
   When I add external electric field to optimize the structure .It runs very very slower than not add the electric field , after 2 days ,the output file is still as following :
 
 iteration #  1     ecut=    30.00 Ry     beta=0.20
     Davidson diagonalization with overlap
     ethr =  1.00E-02,  avg # of iterations =  4.4
 PAY ATTENTION: EL FIELD AND OCCUPATIONS
     Expectation value of exp(iGx):
 (2.751012649613009E-016,-3.679346535033460E-017)  0.866025403784439
     Electronic Dipole per cell (a.u.) -0.482785724081663
     Ionic Dipole per cell (a.u.)   3794.73195575151
 PAY ATTENTION: EL FIELD AND OCCUPATIONS
My input file adhere here:
&CONTROL
                 calculation = 'relax' ,
                restart_mode = 'from_scratch' ,
                  pseudo_dir = './' ,
                      prefix = 'ZnO' ,
                       nstep = 250 ,
                     tprnfor = .true. ,
                    lelfield = .true. ,
                   nberrycyc = 1 ,
                        gdir = 3 ,
 /
 &SYSTEM
                       ibrav = 14,
                   celldm(1) = 18.6286,
                   celldm(2) = 0.6666667,
                   celldm(3) = 1.0733333,
                   celldm(4) = 0,
                   celldm(5) = 0,
                   celldm(6) = -0.5,
                         nat = 48,
                        ntyp = 3,
                     ecutwfc = 30 ,
                     ecutrho = 300 ,
                       nosym = .true. ,
                 occupations = 'smearing' ,
                     degauss = 0.008 ,
                    smearing = 'gaussian' ,
                       nspin = 2 ,
   starting_magnetization(1) = 0.5,
   starting_magnetization(2) = 0.5,
   starting_magnetization(3) = 0.5,
                 lda_plus_u = .false. ,
 /
 &ELECTRONS
                    conv_thr = 1.D-7 ,
                 mixing_mode = 'plain' ,
                 mixing_beta = 0.2 ,
                 startingwfc = 'random' ,
                      efield = 0 ,
 /
 &IONS
                ion_dynamics = 'bfgs' ,
                 phase_space = 'full' ,
 /
ATOMIC_SPECIES
    O   15.00000  O.pbe-rrkjus.UPF
   Zn   65.00000  Zn.pbe-van.UPF
   Mn   54.94000  Mn.pbe-sp-van.UPF
ATOMIC_POSITIONS angstrom
   Zn      0.000000000    1.875966909    0.000000000    1  1  1
    O      0.000000000    1.875966909    1.991601344    1  1  1
....................................................
K_POINTS automatic
  3 3 3   1 1 1
I don't know why after I add the electric field ,the speed of relax is so slow ?
Any advice will be appreciated !

--

Best regards
 
Q.J.Wang
 
XiangTan University 
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