Scanning tunneling microscope (STM) image can be obtained by the Tersoff-Hamann
scheme . The method is nothing but calculation of partial charge
density in an energy window measured from the chemical potential. The calculation
of the partial charge density is performed by the following keywords:
partial.charge on # on|off, default=off
partial.charge.energy.window 0.0 # in eV
where the second keyword defines an energy window (in eV) measured from
the chemical potential (a plus value means conduction band and negative valence).
Since the calculation of the partial charge density is performed during calculation
of the density of states (DOS), the following keywords have to be specified as well:
Dos.fileout on # on|off, default=off
Dos.Erange -20.0 20.0 # default = -20 20
Dos.Kgrid 5 5 5 # default = Kgrid1 Kgrid2 Kgrid3
After the calculation with the keywords, you will get 'System.Name.pden.cube' which can
be used for the STM simulation within the Tersoff-Hamman approximation.
As an example, a simulated STM image of a graphene layer is shown in Fig. 48.
Simulated STM image of a graphene layer, where 'partial.charge.energy.window' of 2 eV was used
in the calculation, and the input file is 'Graphene_STM.dat' in the directory 'work'.
The cube file 'Graphene_STM.pden.cube' was visualized with an isovalue of 0.0001
by a software WSxM .