Re: Enthalpy calculation

From: Jérôme Hénin (
Date: Thu Oct 28 2010 - 11:58:00 CDT

Hi Divya,

You cannot reasonably compute the enthalpy, since the value of U given
by the force field has no absolute meaning because it has an arbitrary
energy reference : only differences between two states of the same
system are meaningful.

However, it might make sense to compute an enthalpy difference between
well-chosen systems. Although in that case, one is more typically
interested in the NPT ensemble, and the change if PV is often
negligible, so what is significant in the end is the change in average
potential energy. The key word here is 'average'.


On 28 October 2010 17:12, divya nayar <> wrote:
> Hi,
> i am simulating (NVT) system of peptide+ water. I want to compute enthalpy
> of this system. Will it be correct to do
> H= U+PV and use the values of potential energy (is it correct to assume it
> to be internal energy?), pressure and volume form the simulation data to
> calculate H?
> Please help.
> Thanks,
> Divya

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