from ATK.TwoProbe import *

# Restore initial density from old calculation
zero_bias = restoreSelfConsistentCalculation("lih2li-scf.nc")

# Create a list of energies from -2 to 5 eV, with 0.1 eV spacing
import numpy 
energy_list = numpy.arange(-2.0, 5.0, 0.1)*electronVolt

# Set k-points for transmission
bz_int_param = brillouinZoneIntegrationParameters( (1,1) )

# Calculate transmission spectrum
trans_spectrum = calculateTransmissionSpectrum(
    self_consistent_calculation = zero_bias,
    energies = energy_list,
    brillouin_zone_integration_parameters = bz_int_param
    )

vnlfile = VNLFile("lih2li_trans.vnl")
vnlfile.addToSample(trans_spectrum,'lih2li')
    
# Define conductance quantum
conductance_quantum = 7.748091733e-5*Siemens

# Calculate transmission spectrum at E_Fermi
fermi_trans = calculateTransmissionSpectrum(
    self_consistent_calculation = zero_bias,
    energies = [0.0]*electronVolt
    )
  
conductance = fermi_trans.coefficients()[0] * conductance_quantum
print 'Zero bias conductance: %.2e Siemens' % (conductance.inUnitsOf(Siemens))