Parameters for calculating transChannel

A transChannel is an incoming Bloch state in the lead of the device. For a given energy, there may be a number of transChannels that may traverse the device scattering region. Parameters here are for calculating the transChannels.

calculation.transChannel.whatDirection

key word	:	calculation.transChannel.whatDirection
possible values	:	1, 2, or 3
default value	:	3
description	:	used for bulk system, to define the transmission
		direction.
		To perform transmission calculation on a perfect
		bulk system, or to analyze transmission channels
		inside a lead, it is necessary to choose one and only
		one of the three central cell vectors as the lead
		direction (i.e. transmission direction); the transverse
		plane is spanned by the other two directions.
an example	:	calculation.transChannel.whatDirection = 3

calculation.transChannel.isAveraged

key word	:	calculation.transChannel.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. obtain 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 storage.
an example	:	calculation.transChannel.isAveraged = 2

calculation.transChannel.kSpaceGridNumber

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

calculation.transChannel.kSpaceGridShift

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

calculation.transChannel.kSpacePoints

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

calculation.transChannel.kPointWeights

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

calculation.transChannel.kPointFile

key word	:	calculation.transChannel.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.transChannel.kPointFile = k-points.dat

calculation.transChannel.energyPoints

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

calculation.transChannel.epsilon

key word	:	calculation.transChannel.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.transChannel.epsilon = 1e-4

calculation.transChannel.plot

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