[Wien] How I can determine the equilibrium interlayer distance between bilayer graphene?

[Peter Blaha]

Probably none of the methods.

The interlayer binding of graphele is maily due to van der Waals forces 
and common GGA functionals do not provide any reasonable binding.

LDA is probably overbinding and a "weak" GGA (WC ?) may give you some 
small binding. Even double minima may occur, ...

Ther's no explicit van der Waals functional in wien2k yet, but even then 
the calculated dond distances and energies would have huge errors.

PS: The potential energy curve is probably VERY flat, so when you want 
to use forces, you would have to converge them to an extremely small 
value, because even with small forces you may be far away from the 
correcponding GGA-minimum.

On 01/25/2014 09:57 PM, Jaafar Jalilian wrote:
>
> We can investigate equilibrium interlayer distance (ID) by two method:
> 1- Using force relaxation at software (miniposition)
> 2- calculating energy versus interlayer distance, and choosing minimum point
> But these methods give different values, for example ID(1)=3.4,
> ID(2)=4.5 angstrom.
> In your opinion, which method provides the correct value?
>
>
> --
> /Sincerely Yours/
>
> Jaafar Jalilian
>
> /Senior Researcher/
> /
> /
> /Young Researchers and Elite Club, Islamic Azad University, Kermanshah,
> Iran./
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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