The ABINIT Users Mailing List ( CLOSED )

[Javier Daniel Fuhr <fuhr@crmcn.univ-mrs.fr>]

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
----------------------------------------------------------

# Si(111) (1x1) surface

iscf 5
occopt 4
fband 0.7
tsmear 0.02

#Optimization of the atomic positions
ionmov  4
ntime  1000

#Definition of the k-point grids
kptopt 1          
ngkpt  8 8 1 

getwfk -1 

#Definition of the unit cell
acell 7.224285 7.224285 53.087437
rprim     1.0000000000E+00  0.0000000000E+00  0.0000000000E+00
         -5.0000000000E-01  8.6602540378E-01  0.0000000000E+00
          0.0               0.0               1.0

#Definition of the atom types
ntypat 1          
znucl 14          

#Definition of the atoms
natom 12          
typat 12*1        
xred              
   0    0    15/72  
   2/3  1/3  17/72
   2/3  1/3  23/72
   1/3  2/3  25/72
   1/3  2/3  31/72
   0    0    33/72
   0    0    39/72  
   2/3  1/3  41/72
   2/3  1/3  47/72
   1/3  2/3  49/72
   1/3  2/3  55/72
   0    0    57/72

#Definition of the planewave basis set
ecut 9.0         

#Definition of the SCF procedure
nstep 30          
toldfe 1.0d-6     
diemac 12.0