[Pw_forum] Van der Walls interaction

[Stefano de Gironcoli]

dispersion interactions, aka vdW, are not included in LAD/GGA/Hybrid  
functionals

this is why DFT-D (switched on by the "london=.true." keyword)  
introduces an empirical damp-dispersion term

interaction between permanent dipoles and the one between permanent  
charges/dipoles and statically induced dipoles is just electrostatic  
and is therefore correctly included in the Hartree term.

Notice that there are new generation of fully non local XC functionals  
vdW-DF, vdW-DF2 and soon VV10 (or actually a refinement of it) that  
are implemented in QE. Check the beginning of Modules/funct.f90 for a  
list of options and some relevant references. As these functionals are  
not implemented in the ld1.x code one needs to force their use by the  
input_dft keyword.. and chose some reasonable, not too different, xc  
functional for the
pseudopotentials.

hope this helps

stefano

Quoting manoj narayanan <manojnarayan86 at gmail.com>:

> 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
>
> On Sun, Aug 12, 2012 at 4:11 PM, Masoud <masoudnahali at gmail.com> wrote:
>
>>
>> Dear Manjo
>>
>> QE can calculate semi-empirical dispersion term, setting "london=.true."
>> you can include such interaction which is weakly calculated by pure DFT in
>> your calculations. I hope it helps.
>> For details please see
>>
>> S. Grimme, J. Comp. Chem. 27, 1787 (2006), and
>> V. Barone et al., J. Comp. Chem. 30, 934 (2009)
>>
>>
>>
>>
>>   Best Wishes, m
>>
>>
>>
>>
>>
>> ----------------------------------------
>> Masoud Nahali
>> SUT
>> masoud.nahali at gmail.com
>> alum.sharif.edu/~m_nahali
>>
>>
>>
>>
>>
>> On Sun, Aug 12, 2012 at 9:37 AM, Manoj wrote:
>>
>>>
>>>
>>> Dear users
>>>                               In my calculation with carbon chain between
>>> 9
>>> to 12 carbon atoms I have to include Van der walls interaction and I am
>>> not
>>> clear about it's inclusion in DFT. What all are the key words
>>> and parameters for that and how effective is the implementation?  Can
>>> anyone shed some light in to this.
>>>
>>> Thanking all in advance
>>> Manoj
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>>
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