How to get the electrode band structure under a certain bias ?

[ATK-user-zuox]

Hello ,every one .For a  spin dependent two-probe  deviceI, i am running  the I-V calculation and  confused about how  to calculate the bandstructure under a certain bias for the electrode after the I-V calculation  .This is my thought: i need to analyse the iv-scf converged device configuration ,but how should i apply it to my left/right electrode ,in another words, how should i write in my code to read the bias left/right electrode configuration and its spin state for my iv-scf converged device configuration  . I can't find any information in the forum and toturial about the detailed items.

Code

# -------------------------------------------------------------
# Bulk Configuration
# -------------------------------------------------------------
 
# Set up lattice
vector_a = [37.2364702358, 0.0, 0.0]*Angstrom
vector_b = [0.0, 23.17211, 0.0]*Angstrom
vector_c = [0.0, 0.0, 9.43074]*Angstrom
lattice = UnitCell(vector_a, vector_b, vector_c)
 
# Define elements
elements = [Sulfur, Sulfur, Sulfur, Sulfur, Molybdenum, Molybdenum, Molybdenum,
            Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Molybdenum,
            Molybdenum, Molybdenum, Molybdenum, Sulfur, Sulfur, Sulfur, Sulfur,
            Sulfur, Sulfur, Sulfur, Molybdenum, Molybdenum, Molybdenum, Sulfur,
            Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Molybdenum,
            Molybdenum, Molybdenum, Molybdenum, Sulfur, Sulfur, Sulfur, Sulfur,
            Sulfur, Sulfur, Sulfur, Molybdenum, Molybdenum, Molybdenum, Sulfur,
            Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Sulfur, Molybdenum,
            Molybdenum, Molybdenum, Molybdenum, Sulfur, Sulfur, Sulfur]
 
# Define coordinates
fractional_coordinates = [[ 0.292994142293,  0.43155327676 ,  0.083333333329],
                          [ 0.439217461613,  0.43155327676 ,  0.083333333329],
                          [ 0.585440780933,  0.43155327676 ,  0.083333333329],
                          [ 0.731664100254,  0.43155327676 ,  0.083333333329],
                          [ 0.34199604229 ,  0.499999999998,  0.083333333329],
                          [ 0.48821936161 ,  0.499999999998,  0.083333333329],
                          [ 0.634442680931,  0.499999999998,  0.083333333329],
                          [ 0.292994142293,  0.568446723236,  0.083333333329],
                          [ 0.439217461613,  0.568446723236,  0.083333333329],
                          [ 0.585440780933,  0.568446723236,  0.083333333329],
                          [ 0.731664100254,  0.568446723236,  0.083333333329],
                          [ 0.366105801953,  0.43155327676 ,  0.249999999997],
                          [ 0.512329121273,  0.43155327676 ,  0.249999999997],
                          [ 0.658552440594,  0.43155327676 ,  0.249999999997],
                          [ 0.26888438263 ,  0.499999999998,  0.249999999997],
                          [ 0.41510770195 ,  0.499999999998,  0.249999999997],
                          [ 0.561331021271,  0.499999999998,  0.249999999997],
                          [ 0.707554340591,  0.499999999998,  0.249999999997],
                          [ 0.366105801953,  0.568446723236,  0.249999999997],
                          [ 0.512329121273,  0.568446723236,  0.249999999997],
                          [ 0.658552440594,  0.568446723236,  0.249999999997],
                          [ 0.292994142293,  0.43155327676 ,  0.416666666664],
                          [ 0.439217461613,  0.43155327676 ,  0.416666666664],
                          [ 0.585440780933,  0.43155327676 ,  0.416666666664],
                          [ 0.731664100254,  0.43155327676 ,  0.416666666664],
                          [ 0.34199604229 ,  0.499999999998,  0.416666666664],
                          [ 0.48821936161 ,  0.499999999998,  0.416666666664],
                          [ 0.634442680931,  0.499999999998,  0.416666666664],
                          [ 0.292994142293,  0.568446723236,  0.416666666664],
                          [ 0.439217461613,  0.568446723236,  0.416666666664],
                          [ 0.585440780933,  0.568446723236,  0.416666666664],
                          [ 0.731664100254,  0.568446723236,  0.416666666664],
                          [ 0.366105801953,  0.43155327676 ,  0.583333333331],
                          [ 0.512329121273,  0.43155327676 ,  0.583333333331],
                          [ 0.658552440594,  0.43155327676 ,  0.583333333331],
                          [ 0.26888438263 ,  0.499999999998,  0.583333333331],
                          [ 0.41510770195 ,  0.499999999998,  0.583333333331],
                          [ 0.561331021271,  0.499999999998,  0.583333333331],
                          [ 0.707554340591,  0.499999999998,  0.583333333331],
                          [ 0.366105801953,  0.568446723236,  0.583333333331],
                          [ 0.512329121273,  0.568446723236,  0.583333333331],
                          [ 0.658552440594,  0.568446723236,  0.583333333331],
                          [ 0.292994142293,  0.43155327676 ,  0.74999999999 ],
                          [ 0.439217461613,  0.43155327676 ,  0.74999999999 ],
                          [ 0.585440780933,  0.43155327676 ,  0.74999999999 ],
                          [ 0.731664100254,  0.43155327676 ,  0.74999999999 ],
                          [ 0.34199604229 ,  0.499999999998,  0.74999999999 ],
                          [ 0.48821936161 ,  0.499999999998,  0.74999999999 ],
                          [ 0.634442680931,  0.499999999998,  0.74999999999 ],
                          [ 0.292994142293,  0.568446723236,  0.74999999999 ],
                          [ 0.439217461613,  0.568446723236,  0.74999999999 ],
                          [ 0.585440780933,  0.568446723236,  0.74999999999 ],
                          [ 0.731664100254,  0.568446723236,  0.74999999999 ],
                          [ 0.366105801953,  0.43155327676 ,  0.916666666657],
                          [ 0.512329121273,  0.43155327676 ,  0.916666666657],
                          [ 0.658552440594,  0.43155327676 ,  0.916666666657],
                          [ 0.26888438263 ,  0.499999999998,  0.916666666657],
                          [ 0.41510770195 ,  0.499999999998,  0.916666666657],
                          [ 0.561331021271,  0.499999999998,  0.916666666657],
                          [ 0.707554340591,  0.499999999998,  0.916666666657],
                          [ 0.366105801953,  0.568446723236,  0.916666666657],
                          [ 0.512329121273,  0.568446723236,  0.916666666657],
                          [ 0.658552440594,  0.568446723236,  0.916666666657]]
 
# Set up configuration
bulk_configuration = BulkConfiguration(
    bravais_lattice=lattice,
    elements=elements,
    fractional_coordinates=fractional_coordinates
    )
 
# Add tags
bulk_configuration.addTags('Left')
 
# -------------------------------------------------------------
# Analysis from File
# -------------------------------------------------------------
bulk_configuration = nlread('ivcurve_selfconsistent_configurations_bias_0.4.nc', object_id='gID000')[0]
 
# -------------------------------------------------------------
# Bandstructure
# -------------------------------------------------------------
bandstructure = Bandstructure(
    configuration=bulk_configuration,
    route=['G', 'Z'],
    points_per_segment=20,
    bands_above_fermi_level=All
    )
nlsave('Device Device-1-7 (1) (left electrode).nc', bandstructure)

. This is my code  and i am not sure if it is right or wrong .

[zh]

If the electrode is  separated from the device, it will means that you are treating a bulk system and that the bias voltage couldn't be applied such bulk system. That is to say, what you will obtain is the band structure of electrode bulk at zero bias voltage. 

The impact of applied voltage on electrode is to shift the Fermi level position of electrode.

"how to calculate the bandstructure under a certain bias for the electrode after the I-V calculation"
It can't be done.

[Jess Wellendorff]

Just to clarify: The concept of a band structure implies a periodic system, which a device configuration is not. The point of a device is exactly that the central region does not extend to infinity along the transport direction. Computing the band structure for a device therefore makes no sense.

What you can do is compute the band structure for the central region only, treating it as a periodic bulk.

For the device, you should consider the DeviceDensityOfStates and ProjectedLocalDDOS analysis modules.

[ATK-user-zuox]

Thank you for your precise correction . .