[Pw_forum] relax question

[xu yuehua]

hello all
i am doing relax.
in my inputfile,
i use  etot_conv_thr=1.D-6
  forc_conv_thr=1.D-6
and the output is
   atom   1 type  1   force =     0.00000290    0.00000095   -0.00000364
     atom   2 type  1   force =     0.00000081   -0.00000108    0.00000033
     atom   3 type  1   force =    -0.00000435   -0.00000425   -0.00000160
     atom   4 type  1   force =    -0.00000312   -0.00000321   -0.00000080
     atom   5 type  1   force =    -0.00000446   -0.00000036   -0.00000273
     atom   6 type  1   force =    -0.00000048    0.00000230    0.00000112
     atom   7 type  1   force =     0.00000164    0.00000118    0.00000060
     atom   8 type  1   force =     0.00000131   -0.00000040    0.00000145
     atom   9 type  2   force =    -0.00000362    0.00000154   -0.00000201
     atom  10 type  2   force =    -0.00000029    0.00000191    0.00000302
     atom  11 type  2   force =     0.00000576   -0.00000134    0.00000194
     atom  12 type  2   force =     0.00000390    0.00000276    0.00000233

Total force =     0.000015     Total SCF correction =     0.000054
     SCF correction compared to forces is too large, reduce conv_thr

     The maximum number of steps has been reached.
my qustion is ,force at every atom is ok ,but why  the program asks to
reduce conv_thr
my conv_thr is not enough small ?
or my total relax step (50) is not adequate?
is there any principle about these parameter?
need your help
thanks a lot
-- 
Xu Yuehua
physics Department of Nanjing university
China
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