[gmx-users] Calculate heat capacity

[Ilya Chorny]

I'm not sure what gromacs does to calc Cv. I get a different reult as well.

Ilya

  -----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 9:53 PM
  To: gmx-users at gromacs.org
  Subject: Re: [gmx-users] Calculate heat capacity


  Hi,
       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.

  Jia-lin

    ----- 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

    Ilya

      -----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


      Hi,
           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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