quantum-espresso/examples/example16

 This example shows how to obtain a simulated STM image of the AlAs(110)
 surface. The image is obtained by  integrating the density of states
 from the bias potential to the fermi energy, as proposed by Tersoff and
 Hamann [PRB 31, 805 (1985)].

1) make a self-consistent calculation for the relaxed AlAs (110) surface
   by using a slab supercell.
   (input=AlAs110re.scf.in, ouput=AlAs110re.scf.out)

2) make a non-self-consistent calculation for the same cell with a larger
   number of k points
   (input=AlAs110re.nonscf.in, output=AlAs110re.nonscf.out)

3) call the postprocessing executable 'pp.x' with the instruction
   'plot_num= 5' to generate the STM simulated image with bias 
   potential specified by 'sample_bias=-0.0735'. Intermediate data 
   is collected in file 'AlAsresm-1.0'. A 2-dimensional slice of 
   the image is then extracted and written to 'AlAs110-1.0'. 
   (input=AlAs110.pp_stm-.in, and output=AlAs110.pp_stm-.out)

4) same as point 3) but with positive bias 'sample_bias=0.0735'.
   Output files: 'AlAsresm+1.0' and 'AlAs110+1.0'. 
   (input=AlAs110.pp_stm+.in, and output=AlAs110.pp_stm+.out)

5-6) produce a postscript file of the simulated STM images by running the
    executable 'plotrho.x'. This generate the PostScript files
    'AlAs110-1.0eV.ps' and 'AlAs110+1.0eV.ps'.
   (input=AlAs110.plotrho-.in, output=AlAs110.plotrho-.out)
   (input=AlAs110.plotrho+.in, output=AlAs110.plotrho+.out)