[molpro-user] ZERO POINT ENERGY

[binjiang.nju]

Dear Peter,

    As far as I understand, you would like to calculate a PES with (harmonic) vibrational energy added at each point. I do not believe that is realistic, unless you are talking about an one dimensional reaction path potential along the reaction coordinate, in which other degrees of freedom are optimized and 3N-7 vibrations are obtained. On a multidimensional PES, otherwise, a normal mode analysis is only physically meaningful at stationary points.

     If the rate constant is of your interest, you can simply calculate the vibrational frequencies at reactant and the transition state, then do the correction and there are some transition state theory codes to perform such calculations.

    I have seen two dimensional minimum energy path surfaces with vibrational energies on the rest of degrees of freedom corrected, reported by the D. C. Clary group. But they have projected out frequencies corresponding to two coordinates in the PES using CURVILINEAR coordinates which are not straghtforward. Just for your reference.

Best, Bin.



Bin Jiang
Department of Chemistry and Chemical Biology
University of New Mexico
Albuquerque, NM, 87106
binjiang.nju at gmail.com
 
From: Martin Spenke
Date: 2014-12-30 09:33
To: Peter.Reinhardt at upmc.fr
CC: Molpro-user at molpro.net
Subject: Re: [molpro-user] ZERO POINT ENERGY
Dear Peter, 

The well-defined problem is that the transition structure 
on an enthalpy surface lacks vibrational energy. 
The usual calculated PES is thus physically an unrealistic surface, therefore 
the whole PES (namely each point) should be vibrationally
corrected, not only for minimum points but for all.

I guess i have to calculate for every single point on a full optimized PES,
ZPEs and add it to electronic energies afterwards to accomplish the physically realistic one.

Bests
Martin 



Peter Reinhardt <Peter.Reinhardt at upmc.fr> schrieb am 10:31 Dienstag, 30.Dezember 2014:


Dear Martin,
I'm not sure whether this is a well-defined problem as the zero-point
energy applies to the minimum around which the PES is expanded in a
quadratic form. ZPE concerns the nuclear motion, not the electronic problem.

Yours,
  Peter

Martin Spenke wrote:
> Dear all, 
> Is it with molpro possible to calculate PES with the inclusion of zero
> point motion corrections to the energy points of the surface at mrci
> level?If yes, what is the keyword for this ?
> BestsMartin_______________________________________________

> Molpro-user mailing list
> Molpro-user at molpro.net
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