FFT

[esp]

I wanted to speed up calculations, and I thought i saw a post somewhere saying i could use the FFT solvers to do this ... i tried it with GNRs but it said that FFT cannot be used when you have gates and dielectrics, which i do .. is this correct?  if i can use fft solvers to speed up calcs for graphene ... can i see an example script?

[Anders Blom]

Use FFT for periodic systems, multigrid for any system - bulk/molecules/devices - with gates or charge, and the special FFT2D for devices without gates. Anything else will not work or give wrong results.