[QE-users] scf of orthorhombic structure

[Pooja Vyas]

Thank you. It helped.

On Wed, Oct 27, 2021 at 3:35 PM Davide Ceresoli <davide.ceresoli at cnr.it>
wrote:

> Dear Pooya Vyas,
> for perovskites, it is customary to report the volume per
> unit formula, in order to compare different polymorphs.
> The Pbnm, Pnma etc... have 4 unit formula. Pm-3m has 1 unit
> formula, etc...
>
> Best.
> D.C.
>
>
> On 10/26/21 12:19 PM, Pooja Vyas wrote:
> > Then according to it, shouldn't I be using the formula V=abc?
> >
> > On Tue, Oct 26, 2021 at 3:47 PM Pooja Vyas <poojavyas595 at gmail.com
> > <mailto:poojavyas595 at gmail.com>> wrote:
> >
> >     Dear user,
> >     my lattice parameters are in agreement with
> >     https://materialsproject.org/materials/mp-560885/
> >     <https://materialsproject.org/materials/mp-560885/>. For which I've
> used
> >     ibrav=8 which is for primitive.
> >
> >     On Tue, Oct 26, 2021 at 3:35 PM Kazume NISHIDATE <
> nisidate at iwate-u.ac.jp
> >     <mailto:nisidate at iwate-u.ac.jp>> wrote:
> >
> >
> >         I don't know what type of primitive vectors you are choosing,
> but the
> >         difference of the volumes may originate from the difference of
> their
> >         definitions.
> >
> >         The simple orthorhombic Bravais lattice is identical to the
> >         conventional cell with the volume of V=abc. While the volume of
> the
> >         primitive face-centered orthorhombic unit cell is V=abc/4.
> >         In your system, 45x4 => 180 is close to your value of 176.
> >
> >         see eg.
> >
> http://aflowlib.org/prototype-encyclopedia/orthorhombic_lattice.html
> >         <
> http://aflowlib.org/prototype-encyclopedia/orthorhombic_lattice.html>
> >
> >         best regards
> >         kazume NISHIDATE
> >         敬具 西館数芽
> >
> >         nisidate at iwate-u.ac.jp <mailto:nisidate at iwate-u.ac.jp>
> >         kazume.nishidate at gmail.com <mailto:kazume.nishidate at gmail.com>
> >
> >
> >         2021年10月26日(火) 17:52 Pooja Vyas <poojavyas595 at gmail.com
> >         <mailto:poojavyas595 at gmail.com>>:
> >
> >             Dear users,
> >
> >             I required optimized lattice parameters of orthorhombic
> CaSiO3 for
> >             which I executed variable cell relaxation. The equilibrium
> volume
> >             obtained was 176 ang^3 while the reported ones are around 45
> ang^3.
> >             The optimized lattice constant agrees well with reported
> data. Can I
> >             know how to convert lattice parameters a, b, c of
> orthorhombic
> >             CaSiO3 into volume?
> >
> >             Also If I require a lattice constant-energy curve, should I
> change
> >             all lattice constants a, b, and c with equal step size and
> run an
> >             scf at all points?
> >
> >             Regards.
> >             _______________________________________________
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>
> --
> +--------------------------------------------------------------+
>    Davide Ceresoli
>    CNR - Istituto di Scienze e Tecnologie Chimiche (SCITEC)
>    c/o University of Milan, via Golgi 19, 20133 Milan, Italy
>    Email: davide.ceresoli at cnr.it
>    Phone: +39-02-50314276, +39-347-1001570 (mobile)
>    Skype: dceresoli
>    Website: http://sites.google.com/site/dceresoli/
> +--------------------------------------------------------------+
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