the density has the dimensions of a density, both is real and reciprocal
space.
rho(G) = 1/\Omega \int rho(r) exp(-iGr) d3r
rho(r) = sum_G rho(G) exp(+iGr)
\Omega being the unit cell volume.
stefano
On 26/07/2016 18:54, Yu,Yue wrote:
Dear all,
I encountered a problem when trying add a extra term rho_extra(G) into
hartree energy calculation (which is done by subroutine v_h in
PW/src/v_of_rho.f90). Here rho(G) means density of charge in G space,
which is generated from rho(r) by doing FFT.
Thus, I need to transfer my known rho_extra(r) (extra charge
distribution needed) to corresponding rho(G) by doing FFT with hand,
the problem is, I have no idea with the standard of FFT set by Quantum
Espresso.
It is important to find how to properly get the rho(G) from rho(r) in
the same way as QE do.
For example, how does Quantum Espresso set the normalization factor
for FFT in a supercelll with volume=V? (It could be put into rho (G)
as 1/V, or into rho(r) as 1/V, or into both rho(g) and rho(r) as
1/sqrt(V)).
I will appreciate if you can offer any help.
Thanks a lot !
Best,
Yue Yu
========================================
Yue Yu
Ph. D student
Department of Physics, University of Florida
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