BSEPREC

BSEPREC = Low | Medium | High | Accurate
Default: BSEPREC = Medium

Description: BSEPREC determines the precision of the time-evolution algorithm for solving the Bethe-Salpeter or Casida equations, i.e., the timestep and the number of steps.

The timestep in the time-evolution calculation is inversely proportional to the maximum transition energy OMEGAMAX and the number of steps is inversely proportional to the broadening CSHIFT. Depending on the BSEPREC stable these parameters are scaled depending on the precision tag BSEPREC.

BSEPREC	OMEGAMAX	CSHIFT
Accurate (a)	$\times 4$	$\times 1/10$
High (h)	$\times 3$	$\times 1/7.5$
Medium (m)	$\times 2.5$	$\times1/6.25$
Low (l)	$\times 2$	$\times1/5$

For example, the number of steps $N_{\rm steps}$ for BSEPREC = Low can be found via $N_{\rm steps}=\frac{{\rm OMEGAMAX}\times 2}{{\rm CSHIFT}/5}$

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