# 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

keyword: 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.

an example:

```calculation.acConductance.maximumFrequency = 1000000
```

## calculation.acConductance.numberOfFrequencyPoints

keyword: calculation.acConductance.numberOfFrequencyPoints

possible values: an integer number

default value: 101

description: number of the frequency points at which the ac conductance is calculated.

an example:

```calculation.acConductance.numberOfFrequencyPoints = 501
```

## calculation.acConductance.temperature

keyword: 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.

description: temperature used in the Fermi function when calculating the acConductance, in unit of Kelvin. Note: the Boltzmann constant k = 8.617342e-05(eV/K) = 3.1668151e-06 (Hartree/K).

an example:

```calculation.acConductance.temperature = 100
```

## calculation.acConductance.kSpaceGridNumber

keyword: calculation.acConductance.kSpaceGridNumber

possible values: 3 x 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: number of small k-space grids in each direction which, together with kSpaceGridShift, are used to produce the parameter kSpacePoints.

an example:

```calculation.acConductance.kSpaceGridNumber = [10 10 10]'
```

## calculation.acConductance.kSpaceGridShift

keyword: calculation.acConductance.kSpaceGridShift

possible values: 3 x 1 or 1 x 3 array, [s_1, s_2, s_3], with each s_i a double number between 0 and 1.

default value: if the acConductance.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.acConductance.kSpaceGridShift = [1/2 1/2 1/2]'
```

## calculation.acConductance.kSpacePoints

keyword: calculation.acConductance.kSpacePoints

possible values: 3 x n double array

default value: defined in the k-point file if the file is given by the parameter acConductance.kPointFile, or produced by the parameters acConductance.kSpaceGridNumber and acConductance.kSpaceGridShift.

description: the fractional coordinates of n transverse wavevectors which are used in the k-space integration.

an example:

```calculation.acConductance.kSpacePoints = [0 0 0]'
```

## calculation.acConductance.kPointWeights

keyword: calculation.acConductance.kPointWeights

possible values: 1 x n double array

default value: defined in the k-point file if the corresponding parameter acConductance.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.acConductance.kPointWeights = [1/2 1/3 1/6]
```

## calculation.acConductance.kPointFile

keyword: 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.

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. The following is an example of the file.

number k1 k2 k3 divisor weight 1 0 0 0 7 1.0 2 0 1 0 7 2.0 3 0 2 0 7 2.0 4 0 3 0 7 2.0 5 1 0 0 7 2.0 6 1 1 0 7 4.0 7 1 2 0 7 4.0 8 1 3 0 7 4.0 9 2 0 0 7 2.0 10 2 1 0 7 4.0 11 2 2 0 7 4.0 12 2 3 0 7 4.0 13 3 0 0 7 2.0 14 3 1 0 7 4.0 15 3 2 0 7 4.0 16 3 3 0 7 4.0

an example:

```calculation.acConductance.kPointFile = 'k-points.dat'
```

## calculation.acConductance.numberOfEnergyPoints

keyword: 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.

an example:

```calculation.acConductance.numberOfEnergyPoints = 100
```

## calculation.acConductance.energyInterval

keyword: calculation.acConductance.energyInterval

possible values: a double number

default value: minmum(50meV, maximum(5meV, kT))

description: Energy interval used to determine the parameter numberOfEnergyPoints.

an example:

```calculation.acConductance.energyInterval = 1e-3
```

## calculation.acConductance.etaSigma

keyword: 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.

an example:

```calculation.acConductance.etaSigma = 1e-4
```

## calculation.acConductance.etaGF

keyword: calculation.acConductance.etaGF

possible values: a small double number

default value: 0

description: the small eta used in the calculation of Green’s function when the ‘GreenFunction’ method is chosen.

an example:

```calculation.acConductance.etaGF = 1e-4
```

## calculation.acConductance.eta

keyword: 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 Green’s function when the ‘GreenFunction’ method is chosen. This parameter is only used when the parameter acConductance.etaSigma and/or acConductance.etaGF is not given.

an example:

```calculation.acConductance.eta = 1e-4
```

## calculation.acConductance.plot

keyword: 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
```