[Pw_forum] SCF loop fails to converge when tefield is switched on

[soroush pakseresht]

Dear all,

I'm trying to do finite electric field calculation for a thin slab with
hexagonal symmetry. I consider a saw-like electric field (as large as 0.0005
au~0.03 eV/A) exerted along c-axis of my hexagonal unit cell. My input
settings (partly) are as follows:

 &CONTROL
                       title = Ta_slab ,
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                      outdir = './tmp/' ,
                  pseudo_dir = './' ,
                      prefix = 'tao' ,
                     tstress = .true. ,
                     tprnfor = .true. ,
                     tefield = .true. ,
                    dipfield = .true. ,

 /
 &SYSTEM
                       ibrav = 4,
                   celldm(1) = 6.90415879,
                   celldm(3) = 21.57221207,
                         nat = 18,
                        ntyp = 3,
                     ecutwfc = 50 ,
                    noncolin = .true. ,
                    lspinorb = .true. ,
                        nbnd = 152,
                        edir = 3 ,
                        eamp = 0.0005834 ,
                     emaxpos = 0.75 ,
                      eopreg = 0.4  ,
 /
 &ELECTRONS
                    conv_thr = 1.0d-6 ,
.
.
.

Using these settings, the calculation appears to be going well for the first
few iterations with rather sharp convergence in total energy, but then it
becomes slower and slower and eventually ends up with a dE much larger than
 conv_thr. Without electric field, there is no such a problem. Any idea how
to improve the SCF convergence while tefield is on?

Any help is appreciated,
Sincerely
-- 
Soroush Pakseresht
Advanced Science Institute (RIKEN)
Saitama-Japan
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