[gmx-users] Velocity autocorrelation
Ignacio Fernández Galván
jellby at yahoo.com
Sun Apr 1 20:05:21 CEST 2012
--- On Sun, 1/4/12, David van der Spoel <spoel at xray.bmc.uu.se> wrote:
> It depends what you want to compare to.
Fair enough. For the moment I don't want to compare to anything. I just want to extract a number of uncorrelated configurations from the simulation, and to know what's the minimum interval at which I should sample configurations.
Something like what's explained in pp. 164-ff of this book:
http://books.google.es/books?id=GT9oPnAEkEQC
> The relaxation time of a
> velocity averaged per atom can be analyze by fitting the vac
> to y = exp(-t/tau). This gives 5 fs in your graph.
5 fs? Don't you mean 5 ps? In that case, how do arrive to such value? It can't be a simple exponential fit, because the function is oscillating. Do you just guess it by the way the amplitude shrinks?
This is my main problem, I don't see how one can fit an exponential to an oscillating function.
Thank you,
Ignacio
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