[Pw_forum] Bond dissociation energy of CO (gas-phase)

[Ameya Joshi]

Hi all,

First of all Axel : using a much greater cutoff (90 Ryd) with BLYP, the BDE 
increased by 20 kcal/mol (!!) to 264 kcal/mol, bringing the value within 8 
kcal/mol of the experimental. Thanks for your valuable input ! I'll try 
increasing the cutoff for other pseudos as well and report if there is any 
improvement. Also I plan to increase the cutoff further with BLYP and check 
for convergence and hopefully a further improvement in the BDE value.

Miguel, the vibrational frequency of CO is about 2200 cm-1, which relates to 
a zero-point correction of 3.1 kcal/mol (ZPE = 0.5*h*nu), so that is 
definitely not the reason for the huge discrepancy.

Prasenjit, I did try the settings you suggested, but got a BDE of 271.6 
kcal/mol (the only change between your input file and mine was a upward 
revision of ecutrho, and the BDE changed by only 0.1 kcal/mol).

Thanks everyone for your inputs.


----- Original Message ----- 
From: "Miguel Martínez Canales" <wmbmacam at lg.ehu.es>
To: <pw_forum at pwscf.org>
Sent: Thursday, September 07, 2006 8:50 AM
Subject: Re: [Pw_forum] Bond dissociation energy of CO (gas-phase)


> Hello everybody,
>
> I have a small naive question with respect to the discrepancies Ameya is 
> getting. Being C and O pretty light elements, and because the dissociation 
> energies he is getting is always (except for BLYP) around 10-15 kcal/mol, 
> ¿could this be caused because he is neglecting the zero-point energy?
>
> -- 
> ----------------------------------------
> Miguel Martínez Canales
>    Dto. Física de la Materia Condensada
>    UPV/EHU
>    Facultad de Ciencia y Tecnología
>    Apdo. 644
>    48080 Bilbao (Spain)
> Fax:  +34 94 601 3500
> Tlf:  +34 94 601 5437
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>
>
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>
> Linus Torvalds
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