[gmx-users] Heat Capacity Question

[Fabian Casteblanco]

Hello,

I am trying to compare the heat capacity (at NPT) of 1000 molecules of
methanol.  I ran it all to equilibrium and used g_energy and -nmol 1000 to
calculate the heat capacity.  The value I achieved, ~140 J/mol*K is far from
what I see is 79.5 J/mol.  I have read on some past posts that there was
some bug in calculating heat capacity but I'm not sure if that applies.  I
tried plotting Enthalpy vs Temp inorder to get dH/dT since that should be
equal to heat capacity but I'm getting ~140 J/mol*K.  I'm not sure if I need
to include the number of constraints and how would I do that.  I used
constr=all-bonds.  Is there something I'm doing wrong?  when it says 140
J/mol*K, it is per mole of what?  I had calculated heat of vaporization
using E<pot>g - Epot<liq>+RT=Hvap and I got it close to the experimental
value (34.09 compared to 35.2 kJ/mol).

Thanks for the help.


-- 
*Best regards,*
**
*Fabian F. Casteblanco*
*Rutgers University -- *
*Chemical Engineering PhD Student*
*C: +908 917 0723*
*E:  **fabian.casteblanco at gmail.com* <fabian.casteblanco at gmail.com>
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