[Pw_forum] about neb

[Cyrille Barreteau]

Just a small comment concerning the question of Rongqin woo.
What do you mean by overestimated? Does it mean you have
an experimental result and the value you find with pwscf is too
high? In anyway I would  be surpised that taking into account
the vibrational zero point energy would make a huge difference.
However as pointed out by Stefano a phonon calculation can give
you access to the prefactor but of course you do not get
quantum tunneling, which can be important for very light atoms.

     cyrille

Stefano de Gironcoli wrote:
> The straightforward, though expensive, way would to compute all phonon
> frequencies for the initial state and for the saddle-point (discarding
> the imaginary one) using the phonon code . This should give you also the
> prefactor.
> Beware however that in this way you are not including quantum tunneling,
> though.
> 
> If you find a better way everybody would be interested.
> 
> stefano
> 
> Wu Rongqin wrote:
> 
> 
>>Dear all,
>>
>>I used the nudged elastic band method to calculate the energy barrier
 and reasonable results can be obtained. however, it is overestimated,
 I have to do correlation for vibrational zero point energy. Is it possible？
  If yes, then how？
>>Thanks 
>>Rongqin woo
>> 
>>
> 
> 
> 
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