View source for O atom spinpolarized low symmetry

{{Template:At_and_mol - Tutorial}}

== Task ==

Performing a spin-polarized low symmetry calculation of a single oxygen atom in a non cubic box to get the right energy minimum.

== Input == 

=== {{FILE|POSCAR}} ===
 O atom in a box
  1.0          ! universal scaling parameters
  7.0 0.0 0.0  ! lattice vector  a(1)
  0.0 7.5 0.0  ! lattice vector  a(2)
  0.0 0.0 8.0  ! lattice vector  a(3)
 1             ! number of atoms
 cart          ! positions in cartesian coordinates
  0 0 0



=== {{FILE|INCAR}} ===
 {{TAGBL|SYSTEM}} = O atom in a box
 {{TAGBL|ISMEAR}} = 0  ! Gaussian smearing
 {{TAGBL|SIGMA}}  = 0.01
 {{TAGBL|ISPIN}} =  2  ! spin polarized calculation

=== {{FILE|KPOINTS}} ===
 Gamma-point only
  0
 Monkhorst Pack
  1 1 1
  0 0 0

== Calculation ==

*In the GGA most atoms are characterized by a symmetry broken solution. VASP, however, symmetrizes the charge density according to the determined symmetry of the cell. Check the {{TAG|OUTCAR}} file, to see what symmetry VASP is using.

*To lower the symmetry, simply change the lattice parameters to 7.0, 7.5 and 8.0 in the {{TAG|POSCAR}} file (see the example file above) and reduce {{TAG|SIGMA}} to {{TAG|SIGMA}}=0.01 in the {{TAG|INCAR}} file.

*By rerunning VASP one finds a much lower energy:

 vasp.5.4.1 05Feb16 (build Aug 22 2016 16:46:23) complex
 ...   ...   . ..
 DAV:  15    -0.189071145737E+01   -0.29321E-03   -0.39183E-05    48   0.478E-02    0.995E-03
 DAV:  16    -0.189071145737E+01   -0.27775E-03   -0.39294E-05    40   0.290E-02    0.541E-03
 DAV:  17    -0.189104076616E+01   -0.51555E-04   -0.34087E-06    48   0.132E-02    
    1 F= -.18910408E+01 E0= -.18910408E+01  d E =-.309633E-20  mag=     1.9998

== Further things to try ==

*How does the energy change when one decreases {{TAG|SIGMA}} to {{TAG|SIGMA}}=0.01 in the {{TAG|INCAR}} file? Why? 

== Download ==
[[Media:Oatomspinlowsym.tgz|Oatomspinlowsym.tgz]
 
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[[Category:Examples]]