[gmx-users] Enthalpy of vaporization

[Justin A. Lemkul]

Fabian Casteblanco wrote:
> Hello all,
> 
> I am trying to find the enthalpy of vaporization for 7 types of
> alcohols to try to compare to experimental values.  I have all of them
> simulated to equilibrium and I can use g_energy to view the Total
> Energy (both kinetic and potential).  In order for me to find the
> enthalpy of vaporization, is it as simple as just running the NPT
> script again and changing the temperature to that of its boiling point
> and 1 degree K over that?  Would it just be the difference between the
> enthalpy at boiling pt and 1 degree past boiling?
> 
> If anyone could possibly lead me in the right direction I would
> greatly appreciate it.  Thanks for your help.
> 

Use g_energy -nmol on your liquid state to extract potential energy per mole. 
Simulate one molecule in the gas phase (no PBC, all cutoffs equal to zero) and 
extract its potential energy.  Then:

DHvap = <Epot(gas)> - <Epot(liq)> + RT

-Justin

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

-- 
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Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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