[Wien] LDA-GGA and van der Waals

[Osama Yassin]

Thank you Tran

I raised the question because of the follwing statement i found on the
article:

RSC Adv. 2015, 5. 18391: DOI: 10.1039/c4ra16966b

​I came across a statement says " LDA usually overbinds solid and thus
underestimates the lattice constant. However, for many layered materials
where the van der Waals interactions play the important role for the
equilibrium geometry, LDA accidently gives reasonable equilibrium
structural parameters such as lattice constant and inter-layer distance"
[ref 32]

[32] ​​Philipp Haas, Fabien Tran, and Peter Blaha, ​ PHYSICAL REVIEW B79,
085104  2009.

Thanx for alerting me by the article: Testing several recent van der Waals
density functionals for layered structures, J. Chem. Phys. 141, 074708
(2014);

osama
================




On Mon, Mar 9, 2015 at 7:16 PM, <tran at theochem.tuwien.ac.at> wrote:

> No. Formally, both LDA and GGA do not take into account van der Waals
> interactions. vdW interactions are taken into account only with more
> adanced functionals:
> http://scitation.aip.org/content/aip/journal/jcp/141/7/10.1063/1.4893329
>
> On Mon, 9 Mar 2015, Osama Yassin wrote:
>
>  Dear Prof Blaha,
>>
>> With reference to the paper
>>
>> Calculation of the lattice constant of solids with semilocal functionals
>>
>> ​​
>> Philipp Haas, Fabien Tran, and Peter Blaha
>>
>> ​​
>> PHYSICAL REVIEW B79, 085104  2009
>> ​For layred metal dichalcogenides (e. g. WS2), does it sound correct if
>> the
>> difference between the lattice constants obtained by LDA and that obtained
>> GGA ​is equivalent to the lattice contraction due to van der Waals forces?
>>
>>
>> Osama
>> Department of Physics, Faculty of Science
>> Taibah University, A-Madinah Al-Munawarh, K. Saudi Arabia
>> A man would do nothing if he waited until he could do it so well that no
>> one
>> could find fault.​
>>
>
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