[Pw_forum] convergence NOT achieved, stopping

[wangqj1]

 Dear PWSCF users
 When I made the 'scf'of 'O',the convergence is very slow,and at last turn up 'convergence NOT achieved, stopping',my inputfile as following:
 
 &CONTROL
                       title = 'O' ,
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                      outdir = '/root/work/ZnO_0_0_1/O' ,
                      wfcdir = '/root/work/ZnO_0_0_1/O' ,
                  pseudo_dir = '/root/tool/espresso-3.2.3/pseudo/' ,
                      prefix = 'O' ,
               etot_conv_thr = 0.0001 ,
               forc_conv_thr = 0.0001 ,
 /
 &SYSTEM
                       ibrav = 14,
                           A = 6.49854 ,
                           B = 6.49854 ,
                           C = 26.427677 ,
                       cosAB = 0 ,
                       cosAC = 0 ,
                       cosBC = 0.5 ,
                         nat = 16,
                        ntyp = 1,
                     ecutwfc = 30 ,
                     ecutrho = 120 ,
                       nosym = .true. ,
                 occupations = 'fixed' ,
                     degauss = 0.02 ,
 /
 &ELECTRONS
                 mixing_mode = 'plain' ,
             diagonalization = 'david' ,
              diago_full_acc = .false. ,
 /
ATOMIC_SPECIES
    O   16.00000  O.pbe-van_bm.UPF 
ATOMIC_POSITIONS angstrom 
    O      1.624773263    0.573114301    0.485838289    
    O      3.249224094    3.822615460    0.485946263    
    O      4.873764156    0.573115030    0.485836746    
    O      3.249294779    1.804680145    2.723816512    
    O      1.624804430    0.573863860   13.703775132    
    O      3.249230400    3.823233855   13.703791642    
    O      4.873742964    0.573863275   13.703791170    
    O      3.249304260    1.805307421   15.942064019    
    O      6.498493290    3.822459082    0.485574395    
    O      4.873652639    5.054116368    2.724105761    
    O      6.498566063    1.804935512    2.723993591    
    O      8.123380444    5.054113329    2.724106775    
    O      6.498495372    3.823229705   13.703092130    
    O      4.873728849    5.054758560   15.941611312    
    O      6.498573263    1.805673494   15.941687153    
    O      8.123315037    5.054760018   15.941598059    
K_POINTS automatic 
  1 1 1   0 0 0 
What should I do ?
Thanks for your advice!
 
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