[Pw_forum] graphene on BN calculation

[mohamed sabri majdoub]

Thank you Davide for the clarification.

On Wed, Dec 16, 2009 at 6:30 PM, Davide Ceresoli <ceresoli at mit.edu> wrote:

> On Wed, 16 Dec 2009, mohamed sabri majdoub wrote:
>
> > Dear Davide,
> >
> > If I change celldim(1)=1.8897261 (in Bohr radius unit), this means that
> the crystal lattice
> > vectors are in Bohr too (same unit as alat).
> Yes, the lattice vectors must be bohrradius unit.
>
> > Crystal lattice vectors:
> >     v1(1)  v1(2)  v1(3)    ... 1st lattice vector
> >
> >     v2(1)  v2(2)  v2(3)    ... 2nd lattice vector
> >     v3(1)  v3(2)  v3(3)    ... 3rd lattice vector
> > In alat units if celldm(1) was specified or in a.u. otherwise.
> > Am I right? If yes then I need to change the following to Bohr units :
> >
> > CELL_PARAMETERS
> > 8.51980 0.00000 0.00000
> > 0.00000 7.37600 0.00000
> > 0.00000 0.00000 22.6120
> You can change them to bohr units and set celldm(1)=1.0, or
> you leave them unchanged but set celldm(1)=1.8897261.
>
> In any case, the product CELL_PARAMETERS*celldm(1) must always
> match your wanted lattice spacings in bohr units, not in angstrom.
>
> This is in contrast with ATOMIC_POSITIONS, where one can choose
> to enter them in angstrom/bohr/alat/crystal units.
>
> HTH.
>
> Davide
>
>
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