[gmx-users] gmx energy How to calculate heat capacity

[Justin Lemkul]

On 2/21/17 1:32 AM, Jafor Ali wrote:
> Hello,
>
> Im trying to calculate heat capacity but I dont get no output.
>
> I got this from terminal
> You should select the temperature in order to obtain fluctuation properties.
>
> My command line is
> gmx energy -f /Users/Genesis/Desktop/Research/Analysis_rep10/up00659/em.edr
> -o /Users/Genesis/Desktop/Research/Analysis_rep10/up00659/energy.xvg
> -fluct_props -driftcorr
>

You probably didn't make the right selections and you didn't use -nmol.  From 
the gmx energy help information:

"Some fluctuation-dependent properties can be calculated provided the correct
energy terms are selected, and that the command line option -fluct_props is
given. The following properties will be computed:
Property                        Energy terms needed
---------------------------------------------------
Heat capacity C_p (NPT sims):    Enthalpy, Temp
Heat capacity C_v (NVT sims):    Etot, Temp
Thermal expansion coeff. (NPT): Enthalpy, Vol, Temp
Isothermal compressibility:     Vol, Temp
Adiabatic bulk modulus:         Vol, Temp
---------------------------------------------------
You always need to set the number of molecules -nmol. The C_p/C_v computations
do not include any corrections for quantum effects. Use the gmx dos program if
you need that (and you do)."

-Justin

-- 
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

==================================================