[Pw_forum] NEB input cell parameters

[Mitul Mundra]

Thanks a lot, Dr. Mattioli. If this is the case, then I would just go ahead
with a fixed cell relax calculation.

Thanks
Mitul


On Thu, Feb 6, 2014 at 2:08 PM, Giuseppe Mattioli <
giuseppe.mattioli at ism.cnr.it> wrote:

>
> Dear Mitul
> If I remember well you cannot perform NEB calculations in a variable-cell
> framework. You should choose a reasonable set of lattice parameters along
> the whole reaction path.
> HTH
> Giuseppe
>
> On Thursday 06 February 2014 07:36:18 Mitul Mundra wrote:
> > Hello,
> >
> > I need to do NEB calculations for my system. My system consists of Si
> 2*2*2
> > supercell with some Li impurities. Prior to NEB, I am doing a vc-relax
> > calculation to get the minimum energy states for the first and the last
> > images of the NEB. For the vc-relax, I set *ibrav = 1* for the symmetric
> > cubic system. In the results obtained from vc-relax calculation, the
> cubic
> > symmetry of the system is lost and I get the following call parameters
> for
> > the initial and final state in the output file.
> >
> > CELL_PARAMETERS (alat= 20.51108588)
> >    1.011059885  -0.002882944  -0.000008465
> >   -0.002882944   1.011059885   0.000008465
> >   -0.000008492   0.000008492   1.007297719
> >
> > CELL_PARAMETERS (alat= 20.51108588)
> >    1.004932042   0.000000442  -0.000000442
> >    0.000000442   1.004688370   0.000104290
> >   -0.000000442   0.000104290   1.004688370
> >
> > Now, I am confused about my input file for the NEB. I can not just
> directly
> > change the lattice constant by taking the cube root of the new volume
> > obtained. I tried to set* ibrav = 0* and give the cell parameters
> obtained
> > but I can only enter them once (correct me if I am wrong) and thus, can
> not
> > incorporate both the set of cell parameters. I would be extremely
> thankful
> > if anyone could suggest me a way to tackle this difficulty.
> >
> >
> > Thanks
> > Mitul Mundra
> > Final year Dual Degree Student
> > Department of Chemical Engineering
> > IIT Kanpur
>
>
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>    Giuseppe Mattioli
>    CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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