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[Riad Shaltaf <shaltaf@photon.physics.metu.edu.tr>]

Dear Javier Daniel FUHR,

Most probably your problem is related to the lattice parameter, so try
changing acell(by decreasing or increasing) gradually until you get a
relatively small component of Sig(3,3).
you can get a nice information about stress calculations from this paper
"Garcia et al.,Phys. Rev. B48, 17350 (1993)."

Riad Shaltaf
Dept. of Physics
METU


On Fri, 18 Jun 2004, Javier Daniel Fuhr wrote:

> Dear all,
> 
> I try to calculate the surface stress for the simple Si(111) (1x1) 
> surface. The
> problem I have is that I get a residual stress component sigma(3 3) 
> (should be
> zero with full relaxation) which is even larger than the parallel 
> components.
> The input file I used is attached, and I used Troullier-Martins 
> pseudopotential.
> 
> After 39 steps I reach convergence, and the energy and stress in the 
> last steps
> are:
> ------------
> -53.141584232924
> -53.141585430875
> -53.141585528293
> -53.141585532538
> ------------
>   sigma(1 1)= -6.21030607E-07  sigma(3 2)=  0.00000000E+00
>   sigma(1 1)= -6.92423985E-07  sigma(3 2)=  0.00000000E+00
>   sigma(1 1)= -6.63214174E-07  sigma(3 2)=  0.00000000E+00
>   sigma(1 1)= -6.76963881E-07  sigma(3 2)=  0.00000000E+00
> -------------
>   sigma(2 2)= -6.21030606E-07  sigma(3 1)=  0.00000000E+00
>   sigma(2 2)= -6.92423983E-07  sigma(3 1)=  0.00000000E+00
>   sigma(2 2)= -6.63214172E-07  sigma(3 1)=  0.00000000E+00
>   sigma(2 2)= -6.76963879E-07  sigma(3 1)=  0.00000000E+00
> -------------
>   sigma(3 3)=  7.58100203E-06  sigma(2 1)=  0.00000000E+00
>   sigma(3 3)=  8.22962968E-06  sigma(2 1)=  0.00000000E+00
>   sigma(3 3)=  7.93965282E-06  sigma(2 1)=  0.00000000E+00
>   sigma(3 3)=  8.01956025E-06  sigma(2 1)=  0.00000000E+00
> --------------
> I would like to know if someone have experience in this type of 
> calculations.
> I do not know if it is a problem of convergence or there is some problem 
> in the
> stress calculation.
> Thank you for any advise.
> Best wishes,
> Javier
> 
> -- 
> ----------------------------------------------------------
> Javier Daniel FUHR
> CRMCN-CNRS
> Campus de Luminy, Case 913
> 13288 Marseille Cedex 9 - FRANCE
> 
> e-mail: fuhr@crmcn.univ-mrs.fr
> 
> >From France x = 0, from Abroad x = 33
> TEL:  x.6.62.92.28.97
> FAX:  x.4.91.41.89.16
> ----------------------------------------------------------
> 
>