[Octopus-users] Questions on SpecDampMode
alberto.castro at tddft.org
Mon Mar 20 16:23:52 WET 2006
Before taking the Fourier transform of any signal that are finite
in time (such as the dipole obtained in octopus), it is convenient to
"damp" or multiply the signal by a function that is unity for the
beginning of the signal, and goes to zero at the end. It amounts to a
convolution in the frequency domain.
The different damping modes just describe what kind of function is
used: an exponential (Exp[-gamma*t]), a third order polynomial, or a
Gaussian (Exp[-gamma*t^2]). The first case amounts to a convolution with a
Lorentzian function, the third case to a convolution also with a Gaussian,
whereas the second case (third order polynomial) amounts to a convolution
with a complicated function that I no longer remember, but I hope you get
If you do not damp the function you would get lots of signal noise
due to the finiteness of the time interval.
On Sun, 19 Mar 2006, yan jun wrote:
> Dear developers:
> What's the differences between the several SpecDampMode: exponential,
> polynomial and gaussian? How do this DampMode work? Thank you.
> Best wishes!
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