# Parameters for calculating acTransmission coefficients

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

## calculation.acTransmission.acFrequencyRange

keyword: calculation.acTransmission.acFrequencyRange

possible values: an 1 x 2 double array

default value: [0,30]

description: The ac transmission is dependent on the ac frequency. This parameter defines a frequency range, and the ac transmission curve over the range will be calculated. The unit is GHz.

an example:

```calculation.acTransmission.acFrequencyRange = [10 20]
```

## calculation.acTransmission.numberOfFrequencyPoints

keyword: calculation.acTransmission.numberOfFrequencyPoints

possible values: an integer number

default value: 101

description: number of the frequency points at which the ac transmission coefficients are calculated.

an example:

```calculation.acTransmission.numberOfFrequencyPoints = 501
```

## calculation.acTransmission.normalizedAcVoltage

keyword: calculation.acTransmission.normalizedAcVoltage

possible values: an 1 x n double array

default value: [0.1, 1, 10]

description: The ac transmission is also dependent on the ac voltage. This parameter, defined as a dimensionless value of eV/Eph with V the ac voltage and the Eph the photon energy of the corresponding ac frequency, is a normailized ac voltage at which the ac transmission will be calculated.

an example:

```calculation.acTransmission.normalizedAcVoltage = [0.1:0.1:1]
```

possible values: cell array of 1 x 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.acTransmission.leadPairs = {[1,2], [2,1]}
```

## calculation.acTransmission.kSpaceGridNumber

keyword: calculation.acTransmission.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.acTransmission.kSpaceGridNumber = [10 10 10]'
```

## calculation.acTransmission.kSpaceGridShift

keyword: calculation.acTransmission.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 acTransmission.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.acTransmission.kSpaceGridShift = [1/2 1/2 1/2]'
```

## calculation.acTransmission.energyPoints

keyword: calculation.acTransmission.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.acTransmission.energyPoints = 0
```

## calculation.acTransmission.etaSigma

keyword: calculation.acTransmission.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.acTransmission.etaSigma = 1e-4
```

## calculation.acTransmission.etaGF

keyword: calculation.acTransmission.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.acTransmission.etaGF = 1e-4
```

## calculation.acTransmission.eta

keyword: calculation.acTransmission.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 cTransmission.etaSigma and/or acTransmission.etaGF is not given.

an example:

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

## calculation.acTransmission.plot

keyword: calculation.acTransmission.plot

possible values: true or false

default value: false

description: If true, a plot will be given after the calculation.

an example:

```calculation.acTransmission.plot = true
```