[gmx-users] Fluctuation dissipation

Paolo Cerri Paolo.Cerri at mi.infn.it
Wed Feb 15 12:39:47 CET 2006

Dear Gromacs users,

I'm running md simulation of hydrophobic aminoacids in water. I evaluate
the heat capacitance for the system at constant volume by computing the
derivative of the energy with respect to temperature (for which the
ratio Delta E / Delta T provides an estimate if Delta T is small enough)
at T=300
I expect the following relation to hold

<E^2> -<E>^2 |at T=300 == K* T^2 *(Delta E/Delta T)

as stated in the fluctuation dissipation theorem
However I obtain values for the right side of the above equation that
are nearly 4 time larger that the left side. 

Has anybody experienced the same problem?


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