# [Pw_forum] how to consider the "dt" flag during vc-relax

Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu
Tue Oct 23 16:17:43 CEST 2007

```On Tue, 23 Oct 2007, Chaohao Hu wrote:

CH> Wow, the  convergence is good when the "dt" flag is further reduced to 30
CH> considering my special system in which it only contains some light elements.
CH> Thanks Dr. Axel and Cesar again for your suggestion -:)

...and you should also consider cesar's suggestion of setting
the atomic masses all to the same value. with light elements
the relative differences between the atom masses and thus the
speed with which those atoms move differs the most. for the
purpose of getting the right structure the masses don't matter.

cheers,
axel.

CH>
CH> ==========
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 7.01
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 6.21
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 5.28
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 4.38
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 3.39
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 2.40
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 1.49
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 0.61
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.24
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.59
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=   -
CH> 0.00
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.14
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.15
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.21
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.24
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.19
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.15
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.13
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.10
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.07
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.07
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.07
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.07
CH>           total   stress  (Ry/bohr**3)                   (kbar)     P=
CH> 0.03
CH> ...
CH>         Total force =     0.001176     Total SCF correction =     0.000004
CH>         Total force =     0.001374     Total SCF correction =     0.000004
CH>         Total force =     0.001858     Total SCF correction =     0.000006
CH>         Total force =     0.001973     Total SCF correction =     0.000003
CH>         Total force =     0.001762     Total SCF correction =     0.000004
CH>         Total force =     0.001475     Total SCF correction =     0.000004
CH>         Total force =     0.001355     Total SCF correction =     0.000004
CH>         Total force =     0.001877     Total SCF correction =     0.000005
CH>         Total force =     0.001823     Total SCF correction =     0.000003
CH>         Total force =     0.001150     Total SCF correction =     0.000005
CH>         Total force =     0.000929     Total SCF correction =     0.000003
CH>         Total force =     0.000917     Total SCF correction =     0.000002
CH>         Total force =     0.000931     Total SCF correction =     0.000003
CH>         Total force =     0.001003     Total SCF correction =     0.000003
CH>         Total force =     0.000736     Total SCF correction =     0.000002
CH>         Total force =     0.000728     Total SCF correction =     0.000002
CH>         Total force =     0.000749     Total SCF correction =     0.000001
CH>         Total force =     0.000747     Total SCF correction =     0.000002
CH>         Total force =     0.000692     Total SCF correction =     0.000003
CH>         Total force =     0.000751     Total SCF correction =     0.000002
CH>         Total force =     0.000872     Total SCF correction =     0.000002
CH>         Total force =     0.000671     Total SCF correction =     0.000003
CH>         Total force =     0.000723     Total SCF correction =     0.000002
CH>         Total force =     0.000715     Total SCF correction =     0.000003
CH>         Total force =     0.000620     Total SCF correction =     0.000002
CH> ...
CH>
CH> Best regards,
CH> C.H.
CH>
CH>

--
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.

```

More information about the users mailing list