[gmx-users] Calculate heat capacity

Jia-Lin Lo jllo at phy.ncu.edu.tw
Wed Mar 17 06:52:01 CET 2004

     I use your algorithm to test.  The value is much different from 
g_energy's result.
       Your algorithm: ~10^5(KJ/mole * K)
       g_energy : ~ 10( J/mole * K)
I take a look  about gmx  source code. There is one paraghaph about
heat capacity. 
VarT = RMSD(T) * RMSD(T),  kb = 8.31451
factor = nmol*ndf*VarT/(3.0*Temp*Temp)
nmol = 1, ndf = 3
Cv = kb / (2/3 - factor)

It seems has no relationship with energy.  I am confused.


  ----- Original Message ----- 
  From: Ilya Chorny 
  To: gmx-users at gromacs.org 
  Sent: Wednesday, March 17, 2004 12:00 PM
  Subject: RE: [gmx-users] Calculate heat capacity

  The heat capacity is proportional to the second moment (variance) of the energy.
  <sigma(E)^2> = k*T^2*Cv 


    -----Original Message-----
    From: gmx-users-admin at gromacs.org [mailto:gmx-users-admin at gromacs.org]On Behalf Of Jia-Lin Lo
    Sent: Tuesday, March 16, 2004 6:59 PM
    To: gmx-users at gromacs.org
    Subject: [gmx-users] Calculate heat capacity

         I am doing a simple simulation ( protein in water). When I use 
    g_energy to monitor the  energy change, there are several statistical values
    printed on screen. I notice the last line is the heat capacity value. I would
    like to know how does it to be calculated?  Is there any formula for it ?
    I want to write a program to calculate it by myself.  
    Thanks for your help in advance.

    Jialin LO
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