[Pw_forum] relax question

[Ding Xunlei]

Dear Yuehua,

The default number is :
etot_conv_thr=1.D-4
forc_conv_thr=1.D-3

So, 1. Your setting for forc_conv_thr=1.D-6 is too small.
	2. If you do need to set force like that, you need to set etot_conv_thr even smaller, saying 1.D-7.  And also, you need to set conv_thr (for scf) smaller than etot_conv_thr, saying 1.D-8.

Hope it help.

Yours sincerely, 				
Ding
2007-07-13
______________________________________________

======= 2007-07-13 16:27:54 You have written: =======

>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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