Parameters for calculating conductance¶

Parameters here are for calculating conductance of the device.

calculation.conductance.method¶

key word	:	calculation.conductance.method
possible values	:	GreenFunction, WaveFunction
default value	:	GreenFunction
description	:	method used for calculating conductance
an example	:	calculation.conductance.method = GreenFunction

key word	:	calculation.conductance.leadPairs
possible values	:	cell array of 1\(\times\)2 integer array
default value	:	all pairs of leads
description	:	For each pair of leads in the cell, the conductance
		from the first lead of the pair to second lead will be
		calculated.
an example	:	calculation.conductance.leadPairs = {[1,2], [2,1]}

key word	:	calculation.conductance.temperature
possible values	:	a double value
default value	:	the value used in the calculation of the self-consistent
		Hamiltonian, or 0 if an user provided Hamiltonian is used.
description	:	temperature used in the Fermi function when
		calculating the conductance, in unit of Kelvin.
		Note: the Boltzmann constant k = 8.617342e-05(eV/K) = 3.1668151e-06 (Hartree/K).
an example	:	calculation.conductance.temperature = 100

key word	:	calculation.conductance.kSpaceGridNumber
possible values	:	3\(\times\)1 integer array
default value	:	the value of calculation.k_spacegrids.number which was
		used in the Hamiltonian calculation, or [1 1 1] if an
		user provided Hamiltonian is used.
description	:	the small k-space grid number in each direction which,
		together with kSpaceGridShift, are used to produce the
		parameter kSpacePoints.
an example	:	calculation.conductance.kSpaceGridNumber = [10 10 10]

key word	:	calculation.conductance.kSpaceGridShift
possible values	:	3\(\times\)1 or 1\(\times\)3 array, [s\(_1\), s\(_2\), s\(_3\)], with each s\(_i\) a
		double number between 0 and 1.
default value	:	if the conductance.kSpaceGridNumber is given, or if an
		user provided Hamiltonian is used, the default value is [0
		0 0], otherwise the default value is the value of
		calculation.k_spacegrids.shift which was used in the
		Hamiltonian calculation.
description	:	k-space grid point shift. While all s\(_i\) are set to be 0,
		the Gamma point is always among the k-space grid points
		being generated; otherwise, the k-space grid points will
		be shifted s\(_1\), s\(_2\), and s\(_3\) grid lengths along their
		grid vector directions, respectively.
an example	:	calculation.conductance.kSpaceGridShift = [1/2 1/2 1/2]

key word	:	calculation.conductance.kSpacePoints
possible values	:	3\(\times\)n double array
default value	:	defined in the k-point file if the file is given by
		the parameter conductance.kPointFile, or produced by
		the parameters conductance.kSpaceGridNumber and
		conductance.kSpaceGridShift.
description	:	the fractional coordinates of n transverse wave vectors
		which are used in the k-space integration.
an example	:	calculation.conductance.kSpacePoints = [0 0 0]

key word	:	calculation.conductance.kPointWeights
possible values	:	1\(\times\)n double array
default value	:	defined in the k-point file if the corresponding
		parameter conductance.kSpacePoints is using the
		k-values in the same file. Otherwise, equally weighted.
description	:	the weights of the k-space points in the k-space
		integration.
an example	:	calculation.conductance.kPointWeights = [1/2 1/3 1/6]

key word	:	calculation.conductance.kPointFile
possible values	:	a file name
default value	:	no default value
description	:	the name of a file which contains the coordinates of
		k-space points and their corresponding weights.

		A k-point file with n k-points has (n+1) lines: one line
		of headers and n lines of values of the n k-points.
		The headers are:

		number : sequential number of the k-point
		k1, k2, k3 : fractional coordinates of the k-point
		divisor : used to modify k1, k2, and k3 so that the
		real fractional coordinates are
		k1/divisor, k2/divisor, k3/divisor
		weight : relative weights of the k-points for the
		k-space integration. Normalized
		so that sum(weight) = 1.

		where the headers number, divisor, and weight are
		optional.
an example	:	calculation.conductance.kPointFile = k-points.dat

key word	:	calculation.conductance.numberOfEnergyPoints
possible values	:	an integer number
default value	:	determined by parameter energyInterval
description	:	the number of energy points used in the energy space
		integration. This is only used when the
		energyPoints and energyPointWeights
		are not given explicitly.
an example	:	calculation.conductance.numberOfEnergyPoints = 100

key word	:	calculation.conductance.energyInterval
possible values	:	a double number
default value	:	5e-2 eV
description	:	Energy interval used to determine the parameter
		numberOfEnergyPoints.
an example	:	calculation.conductance.energyInterval = 1e-3

key word	:	calculation.conductance.energyPoints
possible values	:	double array
default value	:	determined by nanodcal according to the applied
		voltages, temperature, etc.
description	:	the energy points which are used in the energy space
		integration.
		Note that the energy values are measured from chemical
		potential of a lead having zero applied voltage.
an example	:	calculation.conductance.energyPoints = 0:0.03:3

key word	:	calculation.conductance.energyPointWeights
possible values	:	double array with the same length of energyPoints.
default value	:	no default value if the parameter energyPoints is given
		explicitly. Otherwise, determined by nanodcal according
		to the applied voltages, temperature, etc.
description	:	the weights used in the energy space integration.
		The parameter is only used when energyPoints is given
		explicitly.
an example	:	calculation.conductance.energyPoints = ones(1,101)/3

key word	:	calculation.conductance.etaSigma
possible values	:	a small double number
default value	:	1e-6 Hartree
description	:	the small eta used in the calculation of self-energy
		when the GreenFunction method is chosen.
an example	:	calculation.conductance.etaSigma = 1e-4

key word	:	calculation.conductance.etaGF
possible values	:	a small double number
default value	:	0
description	:	the small eta used in the calculation of Greens
		function when the GreenFunction method is chosen.
an example	:	calculation.conductance.etaGF = 1e-4

key word	:	calculation.conductance.eta
possible values	:	a small double number
default value	:	no default value
description	:	the small eta used in the calculation of self-energy
		and/or Greens function when the GreenFunction method
		is chosen. This parameter is only used when the parameter
		conductance.etaSigma and/or conductance.etaGF is not
		given.
an example	:	calculation.conductance.eta = 1e-4

key word	:	calculation.conductance.epsilon
possible values	:	a small double number
default value	:	1e-9
description	:	used as a criterion of Bloch wave. For a wave with
		wave-vector k, if \|\|exp(ika)\|-1\| < epsilon, where a is
		unit cell length, it is considered as a Bloch wave;
		otherwise it is considered as an evanescent wave.
an example	:	calculation.conductance.epsilon = 1e-4