\\

==== Files we will need ====

For succesful simulation of STM, we will need (except the **STM** code) several files. First of all we'll need the right "Fdata" directory (or the link) at our computation directory. Even this files, we will use:

Atomo_i \\
options.inp \\
scan.inp \\
samplek.kpts \\
struc.inp \\
tip_e_str.inp \\
tip_g_str.inp \\
tip_sample_i_j.inp (interaction_i_j.dat)

Let's have a look on them.

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=== Atomo_i ===

This files contains information about Hamiltonian of each atom of the elementary cell of the sample. Their number is the same like the number of atoms in "*.bas" file (which is not necessary here).
 
 \\
 
=== options.inp ===

Inside this file we have the properties settings of the scanning. \\
The file contains:

  -2.00  2.00  16  0.10   ! E00 (E initial), ERANGE, NEE (n steps), EIMAG (η) 
  0                       ! idos(=1 only DOS, =0 STM calculation, =2 Both) 
  1                       ! TIPOSCAN=(0-scan z,1-scan xy z-const,2-scan constant current) 
  0                       ! ICUTT=1 only a xy line 
  2                       ! MODOSCAN(0=tip orbitals,1=sample orbitals,2=both)
  0                       ! idenomin(1 with denominators) 
  0                       ! ists (=1 compute the STS curve) 
  0                       ! icoupling (=0 old stuff =1 new with fireball format) 
  1000000                 ! energy window for STM (typically 0.4) 

Now the initial energy starts from the exact value, and the energy range are the exact voltage.

**TIPOSCAN** can take three different values: 

• 0 if you want to do a scan in a xy constant height changing the z. \\
• 1 if you want to do the xy scan in constant height. \\
• 2 if you want to do the xy scan in constant current. \\

**ICUTT** can take two values: \\
• 0 if you want to do a complete xy scan. \\
• 1 if you only want the line: (XMIN-XMAX,YMIN-YMAX). \\

**MODO_SCAN** can take three different character values. \\
• Tip: means that you do the trace with tip orbitals. \\
• Sam: means that you do the trace with sample orbitals. \\
• Two: means that you do both calculations. \\

**IDENOMIN** cat take three different values again: \\
• 0: means that you do the calculation without multiple scattering effect involved (faster). 

\\

=== scan.inp ===

At this file there is information about the scanning. The distances are in Angstroms.

  2.500                          ! TIPHEIGHT initial (zmax of the surface atoms+ztip apex) 
  -0.866025 , 0.866025 , 18      ! xmin,xmax,nscanx 
  0.000000 , 0.000000 , 18       ! ymin,ymax,nscany 
  1                              ! maximum number of iterations 
  3 3                            ! ncellx, ncelly (number of cells for writing: x means in the direction of the 1st vector, and y means in the direction of the 2nd)


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=== samplek.kpts ===

The file contains the k-points which will be used for calculations (for the sampling of the k-space). The format is as following:

  2                                  !number of k-points
  1.123456 0.500000 0.000000 0.5     !x,y,z coordinate of the k-point and the statistical weight of this k-point 
  1.123456 -0.500000 0.000000 0.5 


//The important thing is, the k-points must be symmetric, it is not possible to use just 1/2 of symmetric points.//

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=== struc.inp, tip_e_str.inp, tip_g_str.inp, tip_sample_i_j.inp (interaction_i_j.dat) ===

These files are necessary for calculation (and their presence in the directory), but the form of them is noted in the parts above (the [[Sample Hamiltonian]], [[The tip structure]], [[The hoppings]])