On May 1, 2008, at 4:34 AM, Amnon Willinger wrote: > > Let's say that a field is given by an eigenvector A. is there an > algorithm that uses the eigenvector and the reciprocal lattice > vectors and can calculate a derivative of that field according to x > or y - i.e. give back an eigenvector B that represents the > derivative? (won't be a true eigenvector of the original problem of > course, but that is not the point) >
No, MPB doesn't include routines to take arbitrary spatial derivatives of the fields. Of course, you can do this yourself using a finite- difference approximation. If your dielectric function is a smooth function, then in principle you could compute spatial derivatives with exponential accuracy by using MPB's internal planewave representation, but to do so you will have to hack MPB's code. For dielectric functions with discontinuities, you'll get second-order accuracy at best by differentiating planewaves, so you might as well just use a center- difference approximation. Regards, Steven G. Johnson _______________________________________________ mpb-discuss mailing list [email protected] http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
