# BSE_SPECTRUM

Parameters influencing the output of the optical absorption spectrum, i.e. the dynamical dipole polarizability tensor \(\alpha_{\mu,\mu'}(\omega)\) (\(\mu,\mu'\in\{x,y,z\}\)), obtained from a BSE calculation, which is defined as \( \alpha_{\mu,\mu'}(\omega) = \sum_n \frac{2 E^{(n)} d^{(n)}_{\mu} d^{(n)}_{\mu'}} {(\omega+i\eta)^2-\left(\Omega^{(n)}\right)^2} \). The printed file will contain the specified frequency range \(\omega\) and the corresponding imaginary part of the average \(\bar{\alpha}(\omega)=\frac{1}{3}\mathrm{Tr} \left[ \alpha_{\mu,\mu'}(\omega)\right]\) as well as of the elements of \(\alpha_{\mu,\mu'}(\omega)\). [Edit on GitHub]

## Keywords

- SECTION_PARAMETERS

- ETA_LIST

- FREQUENCY_END_POINT

- FREQUENCY_STARTING_POINT

- FREQUENCY_STEP_SIZE

## Keyword descriptions

SECTION_PARAMETERS: logical = F

  Lone keyword: `T`

  Usage: &BSE .TRUE.

  Activates printing of optical absorption spectrum from the BSE calculation. [Edit on GitHub]

ETA_LIST: real[ ] = 1.00000000E-002 [eV]

  Usage: ETA_LIST 0.01 …

  Mentions: ⭐GW + Bethe-Salpeter equation

  List of broadening of the peaks in the optical absorption spectrum. [Edit on GitHub]

FREQUENCY_END_POINT: real = 1.00000000E+002 [eV]

  Usage: FREQUENCY_END_POINT 0

  Last frequency to print in the optical absorption spectrum. [Edit on GitHub]

FREQUENCY_STARTING_POINT: real = 0.00000000E+000 [eV]

  Usage: FREQUENCY_STARTING_POINT 0

  First frequency to print in the optical absorption spectrum. [Edit on GitHub]

FREQUENCY_STEP_SIZE: real = 1.00000000E-001 [eV]

  Usage: FREQUENCY_STEP_SIZE 0.1

  Step size of frequencies for the optical absorption spectrum. [Edit on GitHub]