[CPMD-list] how to get Gibbs Free Energy and Entropy from CPMD calculation

[Jan-Willem Handgraaf]

On Wednesday 15 January 2003 03:12, Rongjian Sa wrote:
> Dear Everyone,
> I want to know how to get Gibbs Free Energy and Entropy from CPMD
> calculation. For other program, the Gibbs Free Energy can be got from
> frequency calculation or molecular dynamics simulation. But I can not get
> the same energy information when I attempt run MD and  Vibrational Analysis
> and Free Energy Calculation. So I wander if who can tell me how to get them
> by CPMD calculation? Any kind help and advice of you will be greatly
> appreciated!

Dear Rongjian Sa,

For gas-phase calculations, this in principle possible from a 'vibrational 
analysis' run with CPMD. However, you have to develop your own program to 
obtain from the molecular vibrations and atomic masses the zero-point energy, 
internal energy, and entropy corrections. To my knowledge this is not in the 
CPMD-code.

For constraint MD with CPMD it is more straightforward since then you can 
simply integrate the force along the reaction path to obtain the free energy 
profile. Note that this energy does not contain the zero-point energy 
correction, since the atoms are treated classically.

Hope this helps somewhat.

Sincerely,

Jan-Willem



-- 
Jan-Willem Handgraaf
Department of Chemical Engineering
University of Amsterdam
Nieuwe Achtergracht 166
1018 WV Amsterdam
The Netherlands

Room: C6.18
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Email: jwh at science.uva.nl