On Thu, 25 Oct 2007, wuqi wrote: > I have a similar question. > I am calculating a PC waveguide mode and the group v by taking dw/dk. > As I decrease the k point step dk, the changing of dw is very small for > the slow light region. > > How can I increase the # of significant point of the calculated > frequencies? > > I am using a control .ctl file and (run-te) command.
To calculate the group velocity, you should use the display-group-velocities command in MPB, which calculates it using an analytical formula rather than by finite differences. (And if you do want to differentiate something by finite differences, you should use the "deriv" function in libctl, which uses Richardson extrapolation as described in e.g. Numerical Recipes.) Steven _______________________________________________ mpb-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
