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 eVwhere 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 Kgrid3After 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. 59.