# cbs keywords

Complex band structure calculator

## cbs.whatDirection

When performing complex-band structure calculation, one and only one of
the three fractional coordinates of wavevectors, k1, k2, and k3, is
allowed to be a complex number, while the other two are real.
whatDirection is used to indicate the complex one. e.g., whatDirection =
2 means that k2 can be a complex number while k1 and k2 are kept real.
The complex-band structure can be expressed as k_para = k_para(e,k_tran)
where k_para is the complex component of the wave vector and e the band
energy, k_tran the transverse components of the wave vector. The
corresponding complex k-vector is k-vector = k1 x b1 + k2 x b2 + k3 x
b3, where b1, b2, and b3 are defined through dot(b_i, a_j) = 2pi x
[delta](){i,j}, and a1, a2, a3 are the central cell vectors defined in
centralCellVectors.

**type**: `scalar`

**default**: `3`

**size**: `1`

**example**: `calculation.cbs.whatDirection = 3`

## cbs.energyRange

This parameter and numberOfEnergyPoints are used to produce the
parameter energyPoints. Note that its values are measured from the Fermi
energy.

**type**: `array`

**size**: `[1,2]`

**example**: `cbs.energyRange = [-10, 10]`

## cbs.numberOfEnergyPoints

This parameter and energyRange are used to produce the parameter
energyPoints.

**type**: `scalar`

**default**: `100`

**example**: `cbs.numberOfEnergyPoints = 200`

## cbs.energyPoints

Determined by energyRange and numberOfEnergyPoints if they are both
given, otherwise 0.

**type**: `array`

**size**: `[inf, 1]`

**example**: `cbs.energyPoints = linspace(-10,10,101)`

## cbs.plot

If true, a plot will be given after the calculation. In the plot, k is
the wavevector for Bloch waves, and kappa is the imaginary part of the
wavevector for evanescent waves.

**type**: `scalar`

**default**: `false`

**example**: `cbs.plot = true`
