Study of temperature variation

[nikilanair]

Dear Sir,
          
           Following is my script to determine the I-V characteristic of CNT. Now I wish to determine the  effect of temperature on the I-V curve .So please help me with the script for three different temperatures.My electrodes as well as the scattering regions are of armchair type.Sir I am not sending you the coordinates as they are exceeding the maximum allowed length.

from ATK.TwoProbe import *
from ATK.MPI import processIsMaster
import ivcurve
import numpy

# Generate time stamp
if processIsMaster():
    import platform, time
    print '#',time.ctime()
    print '#',platform.node(),platform.platform()+'\n'

# Opening vnlfile
if processIsMaster(): file = VNLFile('armchair.vnl')


# Set up electrodes
electrode_configuration = PeriodicAtomConfiguration(
    electrode_cell,
    electrode_elements,
    electrode_coordinates
    )

# Set up two-probe configuration
twoprobe_configuration = TwoProbeConfiguration(
    (electrode_configuration,electrode_configuration),
    scattering_elements,
    scattering_coordinates,
    electrode_repetitions=[[1,1],[1,1]],
    equivalent_atoms=([0,0],[57,196])
    )
if processIsMaster(): nlPrint(twoprobe_configuration)
if processIsMaster(): file.addToSample(twoprobe_configuration, 'twoprobe_configuration')

######################################################################
# Central region parameters
######################################################################
exchange_correlation_type = LDA.PZ

iteration_mixing_parameters = iterationMixingParameters(
    algorithm = IterationMixing.Pulay,
    diagonal_mixing_parameter = 0.1,
    quantity = IterationMixing.Hamiltonian,
    history_steps = 6
)

electron_density_parameters = electronDensityParameters(
    mesh_cutoff = 150.0*Rydberg
)

basis_set_parameters = basisSetParameters(
    type = SingleZeta,
    radial_sampling_dr = 0.001*Bohr,
    energy_shift = 0.01*Rydberg,
    delta_rinn = 0.8,
    v0 = 40.0*Rydberg,
    charge = 0.0,
    split_norm = 0.15
)

iteration_control_parameters = iterationControlParameters(
    tolerance = 1e-05,
    criterion = IterationControl.TotalEnergy,
    max_steps = 50
)

electrode_voltages = (0.0,0.0)*Volt

two_probe_algorithm_parameters = twoProbeAlgorithmParameters(
    electrode_constraint = ElectrodeConstraints.Off,
    initial_density_type = InitialDensityType.EquivalentBulk
)

energy_contour_integral_parameters = energyContourIntegralParameters(
    circle_points = 30,
    integral_lower_bound = 3*Rydberg,
    fermi_line_points = 10,
    fermi_function_poles = 4,
    real_axis_infinitesimal = 0.01*electronVolt,
    real_axis_point_density = 0.02*electronVolt
)

two_center_integral_parameters = twoCenterIntegralParameters(
    cutoff = 2500.0*Rydberg,
    points = 1024
)

######################################################################
# Left electrode parameters
######################################################################
left_electrode_electron_density_parameters = electronDensityParameters(
    mesh_cutoff = 150.0*Rydberg
)

left_electrode_iteration_control_parameters = iterationControlParameters(
    tolerance = 1e-05,
    criterion = IterationControl.TotalEnergy,
    max_steps = 50
)

left_electrode_brillouin_zone_integration_parameters = brillouinZoneIntegrationParameters(
    monkhorst_pack_parameters = (1, 1, 500)
)

left_electrode_iteration_mixing_parameters = iterationMixingParameters(
    algorithm = IterationMixing.Pulay,
    diagonal_mixing_parameter = 0.1,
    quantity = IterationMixing.Hamiltonian,
    history_steps = 6
)

left_electrode_eigenstate_occupation_parameters = eigenstateOccupationParameters(
    temperature = 300.0*Kelvin
)

######################################################################
# Collect left electrode parameters
######################################################################
left_electrode_parameters = ElectrodeParameters(
    brillouin_zone_integration_parameters = left_electrode_brillouin_zone_integration_parameters,
    electron_density_parameters = left_electrode_electron_density_parameters,
    eigenstate_occupation_parameters = left_electrode_eigenstate_occupation_parameters,
    iteration_mixing_parameters = left_electrode_iteration_mixing_parameters,
    iteration_control_parameters = left_electrode_iteration_control_parameters
)

######################################################################
# Right electrode parameters
######################################################################
right_electrode_electron_density_parameters = electronDensityParameters(
    mesh_cutoff = 150.0*Rydberg
)

right_electrode_iteration_control_parameters = iterationControlParameters(
    tolerance = 1e-05,
    criterion = IterationControl.TotalEnergy,
    max_steps = 50
)

right_electrode_brillouin_zone_integration_parameters = brillouinZoneIntegrationParameters(
    monkhorst_pack_parameters = (1, 1, 500)
)

right_electrode_iteration_mixing_parameters = iterationMixingParameters(
    algorithm = IterationMixing.Pulay,
    diagonal_mixing_parameter = 0.1,
    quantity = IterationMixing.Hamiltonian,
    history_steps = 6
)

right_electrode_eigenstate_occupation_parameters = eigenstateOccupationParameters(
    temperature = 300.0*Kelvin
)

######################################################################
# Collect right electrode parameters
######################################################################
right_electrode_parameters = ElectrodeParameters(
    brillouin_zone_integration_parameters = right_electrode_brillouin_zone_integration_parameters,
    electron_density_parameters = right_electrode_electron_density_parameters,
    eigenstate_occupation_parameters = right_electrode_eigenstate_occupation_parameters,
    iteration_mixing_parameters = right_electrode_iteration_mixing_parameters,
    iteration_control_parameters = right_electrode_iteration_control_parameters
)

######################################################################
# Initialize self-consistent field calculation
######################################################################
two_probe_method = TwoProbeMethod(
    electrode_parameters = (left_electrode_parameters,right_electrode_parameters),
    exchange_correlation_type = exchange_correlation_type,
    iteration_mixing_parameters = iteration_mixing_parameters,
    electron_density_parameters = electron_density_parameters,
    basis_set_parameters = basis_set_parameters,
    iteration_control_parameters = iteration_control_parameters,
    energy_contour_integral_parameters = energy_contour_integral_parameters,
    two_center_integral_parameters = two_center_integral_parameters,
    electrode_voltages = electrode_voltages,
    algorithm_parameters = two_probe_algorithm_parameters
)
if processIsMaster(): nlPrint(two_probe_method)

runtime_parameters = runtimeParameters(
    verbosity_level = 10,
    checkpoint_filename = 'a2.nc'
)

voltages=numpy.arange(0.0,1.1,0.2)*Volt

ivcurve.runIVcurve (
    twoprobe_configuration,
    two_probe_method,
    runtime_parameters,
    voltages,
    vnl_filename='armchair.vnl', sample_name='twoprobe_configuration',
    current_k_point_sampling = (1,1),
    current_number_of_points = 500
  )


Thanks,
NIKILA

[Anders Blom]

The temperature is given in the script, so you would just change it to whatever value you want. However, the question is what is meant by "effect of temperature". There is no phonon scattering in ATK, the temperature is only used for broadening the Fermi distribution. This can be used to study thermionic emission, but for that I would strongly recommend using ATK 11.2 or later, since there you can specify the temperature directly for the transmission calculation, which saves a huge amount of time.

[nikilanair]

Dear Sir,

          In some of the research papers they have described that the I-V characteristics do changes with temperature i.e at room temperature the characteristic is different from that at higher temperature.This is what I wish to study with the carbon nanotubes.

[kstokbro]

I recommend that you study the tutorial
http://www.quantumwise.com/documents/tutorials/latest/GrapheneDevice/index.html/
which shows how to study the effect of electron temperature on the I-V characteristics.

[Anders Blom]

If the study you refer to is experimental, then the temperature-dependence is most likely due to phonons, which are not included at this point in ATK.