Hi,(adsbygoogle = window.adsbygoogle || []).push({});

so im attempting to evolve a periodic array of charges into a continuous potential using an FFT in fortran 90. this is, to say the least, beyond my abilities and i need help.

Problem:

i have an array 'Ar( )' of N evenly distributed charges, separated by a distance dx. i am using the FFTpack (available on netlib), of which the relevant subroutine calls are:

initialize the fourier wave

CALL dffti (N,wsave)

do forward FFT

CALL DFFTF (N,R,wsave)

do backward FFT

CALL DFFTB (N,R,wsave)

this is pretty much all i know. my main attempt was to replace N with the size of the array Ar, R with the array that contains the charges ( Ar itself) and wsave with an empty dummy array. but this seems to churn out mainly empty array elements,

any help would be much appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Fortran FFT problem

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**