[QE-users] scf of orthorhombic structure

[Davide Ceresoli]

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.
>             _______________________________________________
>             Quantum ESPRESSO is supported by MaX (www.max-centre.eu
>             <http://www.max-centre.eu>)
>             users mailing list users at lists.quantum-espresso.org
>             <mailto:users at lists.quantum-espresso.org>
>             https://lists.quantum-espresso.org/mailman/listinfo/users
>             <https://lists.quantum-espresso.org/mailman/listinfo/users>
> 
>         _______________________________________________
>         Quantum ESPRESSO is supported by MaX (www.max-centre.eu
>         <http://www.max-centre.eu>)
>         users mailing list users at lists.quantum-espresso.org
>         <mailto:users at lists.quantum-espresso.org>
>         https://lists.quantum-espresso.org/mailman/listinfo/users
>         <https://lists.quantum-espresso.org/mailman/listinfo/users>
> 

-- 
+--------------------------------------------------------------+
   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/
+--------------------------------------------------------------+