[gmx-users] What is wrong with enthalpy?

David van der Spoel spoel at xray.bmc.uu.se
Tue Feb 10 20:21:38 CET 2015

On 2015-02-10 18:58, Igor Shchechkin wrote:
> Dear Gromacs users,
> I have changed from 4.5.3 to 4.6.5 version and then continued
> simulation of Protein+Ligands+water+ions system, having used new
> created .tpr file and .cpt file produced by the latter run of 4.5.3
> version. All went normally, but when I evaluated enthalpy, it appeared
> to jump from -1.16e6 to -0.67e6.
> (Earlier I encountered such phenomenon when changed from 4.5.3 to 4.5.5)
> What is the cause of this?
> Best regards,
> Igor Shchechkin
How did you extract it?
Enthalpy = Total Energy + pV
I think the main change was to store the Enthalpy directly in the energy 
file at some point.
Please try to check whether the total energy is the same.

In general it is not recommended to change software version during a 

David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se

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