# To reproduce results from Paper

# Preparation using VASP
#############################################################

The OMEN input are prepared in the PrepData folder. 

In PrepData run the script "create_symlinks.sh" to create
all necessary symlinks.


## VASP

You need to run the VASP simulations in the following folders 
    
    1. relax
    2. scf
    3. bandstructure
    4. wannier 
    5. dielectric

1. Here a short relaxation is done. Simply run the VASP executable

2. Here a the plane wave functions are determined with high accuracy.
   The KPOINTS file corresponds to the one that reached convergence.
   Make sure to comment the NBANDS parameter first and then run a 
   second simulations (with NELMIN = 5 for convergence) once the charge
   is determined to save simulation time.

3. Here the eigenvalues are calculated on a path. So that they can be
   compared to the results obtained by wannier90 on k-points that are
   not explicitely fitted.

4. Preparation of the wannier inputs. The following keywords need to 
   be added to the INCAR of the scf calculation.
    
   LWAVE = .FALSE.
   LCHARG = .FALSE.

   ALGO = None
   LWANNIER90 = .TRUE.
   LWANNIER_MMN_AMN = .TRUE.

   The wannier90.win file provided corresponds to the one with optimal
   projections. In order to reproduced the results its best to delete
   the unit_cell, atoms_car, kpoints and mp_grid keywords. Sometimes the
   interface between VASP and wannier90 has problems with keywords from
   the wannier90.win file. In most cases simply commenting them suffices. 

5. Calculation of the dielectric constant. The isotropicd dielectric constant
   eps_iso can be calculated as in the following paper

   "Sohier, T et. al. Phys. Rev. B, 2016, 94"

## wannier90
#############################################################

   After the wannier90.mmn, wannier90.amn and wannier90.eig files are created
   by the VASP-wannier90 interface you run the wannier90 tool. Make sure the
   write_hr is set to obtained the wannier90_hr.dat file that contains the 
   Wannier Hamiltonian.


## winterface
#############################################################

    The winterface connects the wannier90 and OMEN tools. Two command files

        - winput_old and winput_new 

    are provided because the tool development continued during this study. The 
    new tool should be used from here on. 

    The main parameters to transfer, if not commented out in winput_old, into 
    the winput_new are

        - xyz
        - C
        - l
        - tol
        
    To obtain the Hamiltonians run

    ltool -iwinput_new
    ltool -hwinput_new

    The files needed for the OMEN simulations are

    - H_3.bin, H_4.bin, H_5.bin  containing the Hamiltonian
    - lattice_dat containing the channel structure
    - ph_mat_par containing material parameters
    
    The last two files may be compared to the ones found in the BinaryData folder.
    Differences may occur due to the latest Version of winterface. The best way
    to be sure of a correct reproduction is to compare the basis of as well as the 
    number of all species of the lattice_dat obtained to the one in the BinaryData folder.
    Note that the basis vector in the confined direction might differ because it is changed
    during the OMEN simulation.

# OMEN
#############################################################

    
    The OMEN simulations are carrier out as follows in the folder SimData/electron
    and SimData/hole

    run1:
            Is used to fit the grid to the poisson solver. Therefore grid.dat is then
            used to adapt tox

    run2:   
            First simulations to fix the OFF-state current. Results in SCATTEL_Id_0.dat
            are used to determine new parameter phi_m.

    run3 and run4 
            
            As the first Simulation to determine the right phi_m iteratively

    Lg_15nm:

            Full IV curve starting from the results found in run4

    Lg_Xnm with X={ 12.5, 10, 7.5, 5}

            Simulating two gate voltages with in the OFF-state domain to extract 
            the subthreshold slope. To achieve this without again determining 
            phi_m the gate voltages are shifted such that the currents are close
            enough to the OFF-state value.

    Transmission_new:

            Ballistic Simulations used to extract the pass factor from the transmission.