# BSE_ITERAT

Parameters influencing the iterative Bethe-Salpeter calculation. The iterative solver has not been fully implemented yet. [Edit on GitHub]

## Keywords

- DAVIDSON_ABORT_COND

- EPS_EXC_EN

- EPS_RES

- FAC_MAX_Z_SPACE

- NUM_ADD_START_Z_SPACE

- NUM_DAVIDSON_ITER

- NUM_EXC_EN

- NUM_NEW_T

- Z_SPACE_ENERGY_CUTOFF

## Keyword descriptions

DAVIDSON_ABORT_COND: enum = EN

  Usage: DAVIDSON_ABORT_COND OR

  Valid values:

  - `EN` Uses energy threshold for successfully exiting solver.

  - `RES` Uses residual threshold for successfully exiting solver.

  - `OR` Uses either energy or residual threshold for successfully exiting solver.

  Desired abortion condition for Davidson solver [Edit on GitHub]

EPS_EXC_EN: real = 2.72113839E-002 [eV]

  Usage: EPS_EXC_EN 0.001

  Threshold for stopping the iteration for computing the transition energies. If the desired excitation energies change by less than EPS_EXC_EN (in eV), the iteration stops. [Edit on GitHub]

EPS_RES: real = 2.72113839E-002 [eV]

  Usage: EPS_RES 0.001

  Threshold for stopping the iteration for computing the transition energies. If the residuals inside the Davidson space change by less than EPS_RES (in eV), the iteration stops. [Edit on GitHub]

FAC_MAX_Z_SPACE: integer = 5

  Usage: FAC_MAX_Z_SPACE 5

  Factor to determine maximum dimension of the Davidson subspace. dimension = (NUM_EXC_EN+NUM_ADD_START_Z_SPACE)*FAC_MAX_Z_SPACE [Edit on GitHub]

NUM_ADD_START_Z_SPACE: integer = 0

  Usage: NUM_ADD_START_Z_SPACE 1

  Determines the initial dimension of the subspace as dim = (NUM_EXC_EN+NUM_ADD_START_Z_SPACE) [Edit on GitHub]

NUM_DAVIDSON_ITER: integer = 100

  Usage: NUM_DAVIDSON_ITER 100

  Maximum number of iterations for determining the transition energies. [Edit on GitHub]

NUM_EXC_EN: integer = 3

  Usage: NUM_EXC_EN 3

  Number of lowest excitation energies to be computed. [Edit on GitHub]

NUM_NEW_T: integer = 1

  Usage: NUM_NEW_T 4

  Number of new t vectors added. Must be smaller/equals (NUM_EXC_EN+NUM_ADD_START_Z_SPACE) [Edit on GitHub]

Z_SPACE_ENERGY_CUTOFF: real = -2.72113839E+001 [eV]

  Usage: Z_SPACE_ENERGY_CUTOFF 60

  Cutoff (in eV) for maximal energy difference entering the A matrix. Per default and for negative values, there is no cutoff applied. [Edit on GitHub]