# Parameters for calculating conductance

Parameters here are for calculating conductance of the device.

## calculation.conductance.method

keyword: calculation.conductance.method

possible values: ‘GreenFunction’, ‘WaveFunction’

default value: ‘GreenFunction’

description: method used for calculating conductance

an example:

```calculation.conductance.method = 'GreenFunction'
```

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 conductance from the first lead of the pair to second lead will be calculated.

an example:

```calculation.conductance.leadPairs = {[1,2], [2,1]}
```

## calculation.conductance.kSpaceGridNumber

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

## calculation.conductance.kSpaceGridShift

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

## calculation.conductance.numberOfEnergyPoints

keyword: calculation.conductance.numberOfEnergyPoints

possible values: an integer number

default value: determined by parameter energyInterval

description: the number of energy points used in the energy space integration. This is only used when the energyPoints and energyPointWeights are not given explicitly.

an example:

```calculation.conductance.numberOfEnergyPoints = 100
```

## calculation.conductance.energyInterval

keyword: calculation.conductance.energyInterval

possible values: a double number

default value: 5e-2 eV

description: Energy interval used to determine the parameter numberOfEnergyPoints.

an example:

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

## calculation.conductance.eta

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

an example:

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

## calculation.conductance.epsilon

keyword: calculation.conductance.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.conductance.epsilon = 1e-4
```