Parameters for calculating IVCurve¶
Parameters here are for calculating current-voltage (IV) characteristics.
calculation.IVCurve.systemObjectStatus¶
key word |
: |
calculation.IVCurve.systemObjectStatus |
possible values |
: |
AllCalculated, AllToBeCalculated |
default value |
: |
AllCalculated |
description |
: |
This parameter indicates calculation status of the |
self-consistent field of the system. |
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If AllCalculated, the Hamiltonian calculation has |
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already been completed under all bias voltages. |
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If AllToBeCalculated, needs to calculate the |
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Hamiltonian before the current-voltage curve |
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calculation. In this case, all input parameters for the |
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Hamiltonian calculation should be included, except the |
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calculation.name which will be given in |
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IVCurve.hamiltonianCalculationName and the |
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system.voltageOfLead# which will be given in |
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IVCurve.leadsVoltages. |
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an example |
: |
calculation.IVCurve.systemObjectStatus = … |
AllToBeCalculated |
calculation.IVCurve.systemObjectFiles¶
key word |
: |
calculation.IVCurve.systemObjectFiles |
possible values |
: |
cell array of strings for file names of the |
calculated system objects |
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default value |
: |
no default value |
description |
: |
only used when systemObjectStatus is AllCalculated. |
an example |
: |
calculation.IVCurve.systemObjectFiles = … |
{./bias1/object.mat, ./bias2/object.mat} |
calculation.IVCurve.hamiltonianCalculationName¶
key word |
: |
calculation.IVCurve.hamiltonianCalculationName |
possible values |
: |
a string which will be used as the parameter |
calculation.name when performing the Hamiltonian |
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calculation. |
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default value |
: |
SCF |
description |
: |
not used when systemObjectStatus is AllCalculated. |
an example |
: |
calculation.IVCurve.hamiltonianCalculationName = SCF |
calculation.IVCurve.leadsVoltages¶
key word |
: |
calculation.IVCurve.leadsVoltages |
possible values |
: |
a cell array of 1 by number of leads. each cell is an |
1 by n double array with n an integer. |
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default value |
: |
no default value |
description |
: |
the bias voltages applied to all leads, in unit of Volt. |
Not used when systemObjectStatus is AllCalculated. |
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Note that the chemical potential shift by application of |
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a bias V is -eV. |
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an example |
: |
calculation.IVCurve.leadsVoltages = … |
{0, -1:0.1:1} |
calculation.IVCurve.leadIndex¶
key word |
: |
calculation.IVCurve.leadIndex |
possible values |
: |
integer array |
default value |
: |
all leads |
description |
: |
Index of those leads whose current is to be calculated. |
an example |
: |
calculation.IVCurve.leadIndex = 2 |
calculation.IVCurve.method¶
key word |
: |
calculation.IVCurve.method |
possible values |
: |
GreenFunction, WaveFunction |
default value |
: |
GreenFunction |
description |
: |
method used for calculating conductance or current. |
an example |
: |
calculation.IVCurve.method = GreenFunction |
calculation.IVCurve.temperature¶
key word |
: |
calculation.IVCurve.temperature |
possible values |
: |
a double value |
default value |
: |
the value used in the calculation of Hamiltonian, or |
0 if an user provided Hamiltonian is used. |
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description |
: |
temperature used in the Fermi function when |
calculating the conductance or current, in unit of K. |
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Note: the Boltzmann constant k = 8.617342e-05(eV/K) = 3.1668151e-06 (Hartree/K). |
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an example |
: |
calculation.IVCurve.temperature = 100 |
calculation.IVCurve.kSpaceGridNumber¶
key word |
: |
calculation.IVCurve.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 |
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user provided Hamiltonian is used. |
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description |
: |
the small k-space grid number in each direction which, |
together with kSpaceGridShift, are used to produce the |
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parameter kSpacePoints. |
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an example |
: |
calculation.IVCurve.kSpaceGridNumber = [10 10 10] |
calculation.IVCurve.kSpaceGridShift¶
key word |
: |
calculation.IVCurve.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. |
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default value |
: |
if the IVCurve.kSpaceGridNumber is given, or if an |
user provided Hamiltonian is used, the default value is [0 |
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0 0], otherwise the default value is the value of |
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calculation.k_spacegrids.shift which was used in the |
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Hamiltonian calculation. |
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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 |
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being generated; otherwise, the k-space grid points will |
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be shifted s\(_1\), s\(_2\), and s\(_3\) grid lengths along their |
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grid vector directions, respectively. |
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an example |
: |
calculation.IVCurve.kSpaceGridShift = [1/2 1/2 1/2] |
calculation.IVCurve.kSpacePoints¶
key word |
: |
calculation.IVCurve.kSpacePoints |
possible values |
: |
3\(\times\)n double array |
default value |
: |
defined in the k-point file if the file is given by |
the parameter IVCurve.kPointFile, or produced by |
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the parameters IVCurve.kSpaceGridNumber and |
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IVCurve.kSpaceGridShift. |
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description |
: |
the fractional coordinates of n transverse wave vectors |
which are used in the k-space integration. |
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an example |
: |
calculation.IVCurve.kSpacePoints = [0 0 0] |
calculation.IVCurve.kPointWeights¶
key word |
: |
calculation.IVCurve.kPointWeights |
possible values |
: |
1\(\times\)n double array |
default value |
: |
defined in the k-point file if the corresponding |
parameter IVCurve.kSpacePoints is using the |
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k-values in the same file. Otherwise, equally weighted. |
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description |
: |
the weights of the k-space points in the k-space |
integration. |
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an example |
: |
calculation.IVCurve.kPointWeights = [1/2 1/3 1/6] |
calculation.IVCurve.kPointFile¶
key word |
: |
calculation.IVCurve.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. |
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A k-point file with n k-points has (n+1) lines: one line |
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of headers and n lines of values of the n k-points. |
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The headers are: |
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number : sequential number of the k-point |
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k1, k2, k3 : fractional coordinates of the k-point |
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divisor : used to modify k1, k2, and k3 so that the |
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real fractional coordinates are |
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k1/divisor, k2/divisor, k3/divisor |
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weight : relative weights of the k-points for the |
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k-space integration. It is normalized |
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so that sum(weight) = 1. |
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where the headers number, divisor, and weight are |
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optional. |
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an example |
: |
calculation.IVCurve.kPointFile = k-points.dat |
calculation.IVCurve.energyInterval¶
key word |
: |
calculation.IVCurve.energyInterval |
possible values |
: |
a double number |
default value |
: |
5e-2 eV |
description |
: |
Energy interval used to determine the parameter |
numberOfEnergyPoints. |
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an example |
: |
calculation.IVCurve.energyInterval = 1e-3 |
calculation.IVCurve.energyPoints¶
key word |
: |
calculation.IVCurve.energyPoints |
possible values |
: |
double array |
default value |
: |
determined by nanodcal according to the applied |
voltages, temperature, etc. |
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description |
: |
the energy points which are used in the energy space |
integration. |
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Note that the energy values are measured from chemical |
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potential of a lead having zero applied voltage. |
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an example |
: |
calculation.IVCurve.energyPoints = 0:0.03:3 |
calculation.IVCurve.energyPointWeights¶
key word |
: |
calculation.IVCurve.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 |
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to the applied voltages, temperature, etc. |
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description |
: |
the weights used in the energy space integration. |
The parameter is only used when energyPoints is given |
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explicitly. |
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an example |
: |
calculation.IVCurve.energyPointWeights = ones(1,101)/3 |
calculation.IVCurve.etaSigma¶
key word |
: |
calculation.IVCurve.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. |
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an example |
: |
calculation.IVCurve.etaSigma = 1e-4 |
calculation.IVCurve.etaGF¶
key word |
: |
calculation.IVCurve.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. |
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an example |
: |
calculation.IVCurve.etaGF = 1e-4 |
calculation.IVCurve.eta¶
key word |
: |
calculation.IVCurve.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 |
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is chosen. This parameter is only used when the |
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parameter IVCurve.etaSigma and/or IVCurve.etaGF is not |
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given. |
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an example |
: |
calculation.IVCurve.eta = 1e-4 |
calculation.IVCurve.epsilon¶
key word |
: |
calculation.IVCurve.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 |
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unit cell length, it is considered as a Bloch wave; |
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otherwise it is considered as an evanescent wave. |
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an example |
: |
calculation.IVCurve.epsilon = 1e-4 |
calculation.IVCurve.plot¶
key word |
: |
calculation.IVCurve.plot |
possible values |
: |
true or false |
default value |
: |
false |
description |
: |
If true, a plot will be given after the calculation. |
an example |
: |
calculation.IVCurve.plot = true |