[Pw_forum] Van der Walls interaction

[Masoud]

Dear Manjo

The forces between two permanent dipoles and a permanent dipole and a
corresponding induced dipole are usually larger than two instantaneously
induced dipoles. So I expect that DFT and especially DFT-D can see the two
first mentioned forces better than the latter. You can make a clever set of
molecules that their Inter-molecular forces change and calculate the energy
once with DFT-D and another time with pure DFT. Then you can understand
that which of the approaches can predict the trend well. You 'd better not
care about absolute values and just check the trend. I hope it helps.



Best Wishes, m





----------------------------------------
Masoud Nahali
SUT
masoud.nahali at gmail.com
alum.sharif.edu/~m_nahali





On Sun, Aug 12, 2012 at 6:06 PM, Manoj wrote:

>
>
>  Dear Masoud
>                              Thank you for your reply, but what my doubt is
> that QE only includes london dispersion. What about other effects like
> Keesom and Debye forces ?
>
> Yours Sincerely
> Manoj
>
>
>
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