BSEPREC: Difference between revisions

Revision as of 10:17, 20 October 2023

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 for BSEPREC = Low can be found $N_{\rm steps}=\frac{{\rm OMEGAMAX}\times 2}{{\rm CSHIFT}\times5^{-1}}$

@@ Line 2: / Line 2: @@
-Description: {{TAG|BSEPREC}} determines the precision for the time-evolution calculation in BSE and TDDFT, i.e., the step size and the number of steps.
+Description: {{TAG|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 {{TAG|OMEGAMAX}} and the number of steps is inversely proportional to the broadening {{TAG|CSHIFT}}. To make the algorithm sufficiently stable these parameters are scaled depending on the precision tag {{TAG|BSEPREC}}.
+The timestep in the time-evolution calculation is inversely proportional to the maximum transition energy {{TAG|OMEGAMAX}} and the number of steps is inversely proportional to the broadening {{TAG|CSHIFT}}. Depending on the {{TAG|BSEPREC}}  stable these parameters are scaled depending on the precision tag {{TAG|BSEPREC}}.
 ::{| cellpadding="5" cellspacing="0" border="1"
 ! BSEPREC !! OMEGAMAX !! CSHIFT
 |-
-| Accurate (a) || &times;4 || &times;10
+| Accurate (a) || <math>\times 4</math> || <math>\times 1/10</math>
 |-
-| High (h) || &times;3 || &times;7.5
+| High (h) || <math>\times 3</math> || <math>\times 1/7.5</math>
 |-
-| Medium (m) || &times;2.5 || &times;6.25
+| Medium (m) || <math>\times 2.5</math> || <math>\times1/6.25</math>
 |-
-| Low (l)  || &times;2 || &times;5
+| Low (l)  || <math>\times 2</math> || <math>\times1/5</math>
 |}
-For example, the number of steps for {{TAG|BSEPREC}} = Low is <math>N_{\rm steps}=\frac{OMEGAMAXx2}{CSHIFTx5}
+For example, the number of steps for {{TAG|BSEPREC}} = Low can be found <math>N_{\rm steps}=\frac{{\rm OMEGAMAX}\times 2}{{\rm CSHIFT}\times5^{-1}}</math>
@@ Line 25: / Line 25: @@
 == Related tag and articles ==
 {{TAG|NBANDSO}},
-[[BSE calculations]],
+[[BSE calculations]]
-[[timepropagation]]
 {{sc|NBANDSV|Examples|Examples that use this tag}}