Hi,
I've never worked with *.MDE files, but to me it looks like your calculation
is not yet converged. You set for a stress of 5 GPa and the last reported value
is 7.973 GPa.
BTW, why do you expect a uniform pressure change ? (the cell is increasing the
volume (while P is going down), overshoots (P becomes negative) and comes back
(P again positive).
Regards,
Roberto
On 12/16/2013 08:10 PM, Kausala Mylvaganam wrote:
Dear Siesta users,
I am trying to do a uniaxial tension/compression using gold as an example.
As explained in section 7.2 of the SIESTA manual I tried this using the
following information in my .fdf file.
****************************************************************************
MD.TargetPressure 5. GPa
%block MD.TargetStress
0.0 0.0 1.0 0.0 0.0 0.0
%endblock MD.TargetStress
****************************************************************************
1). According to the manual to apply compressive stress along z-direction the
third value should be -1.0. But I find that the above data (i.e. +1.0) led to
compression.
i.e. the distance along z-direction decreased (apart from an initial increase
in steps 0-2).
2). On CG optimization my .MDE file look like
****************************************************************************
# Step T (K) E_KS (eV) E_tot (eV) Vol (A^3) P (kBar)
0 0.00 -43507.35440 -43507.35440 813.930 107.229
1 0.00 -43509.79209 -43509.79209 841.537 52.558
2 0.00 -43510.17254 -43510.17254 884.459 -22.055
3 0.00 -43510.25543 -43510.25543 864.915 9.855
4 0.00 -43510.11902 -43510.11902 864.567 7.973
****************************************************************************
I noticed that the pressure change (last coulmn) is not uniform.
I would like to see for every 5 GPa stress change, how the cell parametres are
changing. Could anyone let me know how this can be done.
Thanks.
Best Regards
Kausala
