[gmx-users] specific heat calculation using "gmx dos"

[Pragati Sharma]

 Dear all,

I am trying to calculate heat capacity of a polymeric system (30k atoms)
using gromacs.
I tried the classical way from the fluctuation dependent properties using
"gmx energy", but the values are not matching experimental values.

I want to use "gmx dos" program, but I have some confusions.

1. Does it gives only the quantum corrections in heat capacity, which
should be added to the one calculated from 'gmx energy' or  Does it gives
full heat capacity value including quantum corrections.

2. Should I have to run NVT simulations, run gmx dos, find Cv and the add
then calculate Cp, as given in the paper ( J. Chem. Theory Comput. 2012, 8,
61–74), *OR*
I can run a NPT simulation and calculate Cp from gmx dos.

3. gmx dos gives the Cp/Cv value in "dos.log" file. but is there any output
file to check its convergence. I mean how should I decide, how long the
trajectory I should take.

4. Cp can be calculated from the slope of enthalpy vs temp plot (dH/dT) (in
a small range of temp), what limitation does this approach have.

Thanks in advance.