Parameters for calculating transmission coefficients¶

Parameters here are for calculating the transport coefficients of quantum transport.

calculation.transmission.method¶

key word	:	calculation.transmission.method
possible values	:	GreenFunction or WaveFunction
default value	:	GreenFunction
description	:	method used for the calculation of the transmission
		coefficient.
an example	:	calculation.transmission.method = GreenFunction

key word	:	calculation.transmission.isAveraged
possible values	:	0, 1, 2
default value	:	1
description	:	If 0, the calculated transmission coefficient is
		expressed as a function of both energy and transverse
		k-vector (i.e. gives transmission hot spot).
		If 1, in addition, a k-space average is
		performed on the transmission coefficient, and the
		averaged coefficient is a function of energy only. If 2,
		only the averaged transmission coefficient are kept,
		just for saving disk space.
an example	:	calculation.transmission.isAveraged = 2

key word	:	calculation.transmission.eigenChannelNumber
possible values	:	0 or a positive integer
default value	:	0
description	:	When it is a positive number, the transmission
		coefficient will be projected into the contributions of
		eigen-channels, and this positive integer should be an
		estimated upper-bound of the number of eigen-channels.
		resolved in k-space, instead of integrated over the
		Brillouin zone.
an example	:	calculation.transmission.isProjected = true

key word	:	calculation.transmission.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 transmission
		from the first lead of the pair to the second lead is
		to be calculated.
an example	:	calculation.transmission.leadPairs = {[1,2], [2,1]}

key word	:	calculation.transmission.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.transmission.kSpaceGridNumber = [10 10 10]

key word	:	calculation.transmission.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 transmission.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.transmission.kSpaceGridShift = [1/2 1/2 1/2]

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

key word	:	calculation.transmission.kPointWeights
possible values	:	1\(\times\)n double array
default value	:	defined in the k-point file if the corresponding
		parameter transmission.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.transmission.kPointWeights = [1/2 1/3 1/6]

key word	:	calculation.transmission.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. It is normalized
		so that sum(weight) = 1.

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

key word	:	calculation.transmission.energyPoints
possible values	:	double array
default value	:	chemical potentials of all the leads.
description	:	the energy points at which the transmission will be
		calculated.
		Note that the energy values are measured from chemical
		potential of a lead having zero applied voltage.
an example	:	calculation.transmission.energyPoints = 0

key word	:	calculation.transmission.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.transmission.etaSigma = 1e-4

key word	:	calculation.transmission.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.transmission.etaGF = 1e-4

key word	:	calculation.transmission.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
		transmission.etaSigma and/or transmission.etaGF is not
		given.
an example	:	calculation.transmission.eta = 1e-4

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

key word	:	calculation.transmission.plot
possible values	:	true or false
default value	:	false
description	:	If true, a plot will be given after the calculation.
an example	:	calculation.transmission.plot = true