Parameters for calculating acConductance¶
Parameters here are for calculating the frequency dependent conductance. When an AC bias is applied to the device, frequency dependent transport properties are important. At high AC frequency, induction produces displacement currents which must be taken into account.
calculation.acConductance.maximumFrequency¶
key word |
: |
calculation.acConductance.maximumFrequency |
possible values |
: |
a double number |
default value |
: |
10 THz |
description |
: |
the ac conductance is calculated as a function of |
frequency from zero up to this value. The unit is MHz. |
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an example |
: |
calculation.acConductance.maximumFrequency = 1000000 |
calculation.acConductance.numberOfFrequencyPoints¶
key word |
: |
calculation.acConductance.numberOfFrequencyPoints |
possible values |
: |
an integer number |
default value |
: |
101 |
description |
: |
number of the frequency points at which the ac |
conductance is calculated. |
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an example |
: |
calculation.acConductance.numberOfFrequencyPoints = 501 |
calculation.acConductance.temperature¶
key word |
: |
calculation.acConductance.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. |
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description |
: |
temperature used in the Fermi function when |
calculating the acConductance, in unit of Kelvin. |
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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.acConductance.temperature = 100 |
calculation.acConductance.kSpaceGridNumber¶
key word |
: |
calculation.acConductance.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.acConductance.kSpaceGridNumber = [10 10 10] |
calculation.acConductance.kSpaceGridShift¶
key word |
: |
calculation.acConductance.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 acConductance.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.acConductance.kSpaceGridShift = [1/2 1/2 1/2] |
calculation.acConductance.kSpacePoints¶
key word |
: |
calculation.acConductance.kSpacePoints |
possible values |
: |
3\(\times\)n double array |
default value |
: |
defined in the k-point file if the file is given by |
the parameter acConductance.kPointFile, or produced by |
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the parameters acConductance.kSpaceGridNumber and |
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acConductance.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.acConductance.kSpacePoints = [0 0 0] |
calculation.acConductance.kPointWeights¶
key word |
: |
calculation.acConductance.kPointWeights |
possible values |
: |
1\(\times\)n double array |
default value |
: |
defined in the k-point file if the corresponding |
parameter acConductance.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.acConductance.kPointWeights = [1/2 1/3 1/6] |
calculation.acConductance.kPointFile¶
key word |
: |
calculation.acConductance.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. 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.acConductance.kPointFile = k-points.dat |
calculation.acConductance.numberOfEnergyPoints¶
key word |
: |
calculation.acConductance.numberOfEnergyPoints |
possible values |
: |
an integer number |
default value |
: |
determined by parameter energyInterval |
description |
: |
the number of energy points used in the energy space |
integration. |
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an example |
: |
calculation.acConductance.numberOfEnergyPoints = 100 |
calculation.acConductance.energyInterval¶
key word |
: |
calculation.acConductance.energyInterval |
possible values |
: |
a double number |
default value |
: |
minimum(50meV, maximum(5meV, kT)) |
description |
: |
Energy interval used to determine the parameter |
numberOfEnergyPoints. |
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an example |
: |
calculation.acConductance.energyInterval = 1e-3 |
calculation.acConductance.etaSigma¶
key word |
: |
calculation.acConductance.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.acConductance.etaSigma = 1e-4 |
calculation.acConductance.etaGF¶
key word |
: |
calculation.acConductance.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.acConductance.etaGF = 1e-4 |
calculation.acConductance.eta¶
key word |
: |
calculation.acConductance.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 parameter |
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acConductance.etaSigma and/or acConductance.etaGF is not |
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given. |
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an example |
: |
calculation.acConductance.eta = 1e-4 |
calculation.acConductance.plot¶
key word |
: |
calculation.acConductance.plot |
possible values |
: |
true or false |
default value |
: |
false |
description |
: |
If true, a plot will be given after the calculation. |
an example |
: |
calculation.acConductance.plot = true |