Heat capacity using gmx energy command

User discussions
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1

GROMACS version: 2021
GROMACS modification: No

Hi all,

I am using “gmx energy” to calculate the heat capacity of water (TIP4P/2005 water model) by using the following the command;

gmx energy -f em.edr -o energy.xvg -fluct_props -nmol 851 -driftcorr

To obtain the C_p, (NPT simulation), I have selected enthalpy and temperature.

However, I am not getting very lower C_p value . It is approximately 3 times lower than what is available on literature.

Please let me know If I am making any mistake or missing something.

Regards,
Sheeba

2

3 times lower than in literature for TIP4P/20005 or for real water?

TIP4P/2005 has no internal degrees of freedom. This means the number of degrees of freedom is a factor 3 lower which results in a heat capacity which is roughly a factor 3 lower.

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for real water. I was trying to compare the results with experiments.