Re: [QE-users] Simple cubic to fcc cubic

[Giovanni Cantele]

I would add, to support this suggestion, that this forum is, in my opinion,
a very precious resource, for both those who are beginners and those who
are less beginners
because not only there is a more than reasonable response "rate" to posed
problems and questions but also, browsing past threads, you might discover
lot of
tricks, explanations, suggestions that might result helpful for you!
Giovanni

-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cant...@spin.cnr.it 
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno mar 27 feb 2024 alle ore 11:46 Stefano Baroni 
ha scritto:

> Thank you Giovanni. May I suggest that in this and other similar cases
> help from the Quantum ESPRESSO Community is properly acknowledged in any
> work (thesis, paper, report) that has benefited from it? Thanks — Stefano
>
>
> On 27 Feb 2024, at 11:36, Giovanni Cantele 
> wrote:
>
> Let us suppose that we have a fcc crystal, with one atom per cell, at
> (0,0,0), for the sake of simplicity.
>
> The unit cell sides are in the form (a/2,a/2,0) (a=side of the cubic
> cell), with unit cell volume a^3 / 4.
>
> Now, let us move from fcc to sc unit cell.
> Each of the 8 atoms at the corners is shared by 8 cubic cells, and thus we
> should consider only one of these atoms.
> On the other hand, atoms at the center of the cube faces are shared by two
> unit cells, and count as 1/2. Since we have
> 6 faces, 3 out of these 6 atoms must be considered.
> As a result, the sc unit cell will contain 4 atoms and a volume 4 times
> larger, a^3 as you would expect.
>
> To go back from sc to fcc you should therefore keep 1/4 of your atoms,
> because those that are associated to the centers of three faces,
> that should be explicitly considered in sc, now become equivalent (that
> is, connected by a lattice vector) to other atoms in fcc.
>
> The code correctly finds overlapped atoms, e.g. in the example of one atom
> per unit cell, in sc you would have (0,0,0), (a/2,a/2,0), (a/2,0,a/2),
> (0,a/2,a/2)
> and the last three in fcc are obtained from (0,0,0) after a lattice
> translation by (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2), respectively.
>
> Giovanni
>
> --
>
> Giovanni Cantele, PhD
> CNR-SPIN
> c/o Dipartimento di Fisica
> Universita' di Napoli "Federico II"
> Complesso Universitario M. S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> e-mail: giovanni.cant...@spin.cnr.it 
> Phone: +39 081 676910
> Skype contact: giocan74
>
> ResearcherID: http://www.researcherid.com/rid/A-1951-2009
> Web page: https://sites.google.com/view/giovanni-cantele/home
>
>
> Il giorno mar 27 feb 2024 alle ore 11:14 Ms. Chandrika K. via users <
> users@lists.quantum-espresso.org> ha scritto:
>
>> Need help in understanding
>>
>>1. I am currently working on Co3O4 structure,from literature it is
>>very evident that it belongs to space group Fd3m(cubic fcc).
>>2. I have referred to Co3O4 Fd3m cubic structure from materials
>>project it is represented as simple cubic structure but Fd3m space group
>>refers to cubic fcc.
>>3. As it is simple cubic ibrav =1,when i change ibrav =2(cubic fcc) i
>>am getting warning message
>>"WARNING: Atom 381 and atom 444 are very close !!!   Atom 444 deleted
>>!!!"
>>ATOMIC_POSITIONS (angstrom)
>>
>> I would like to know how to change the structure from simple cubic to fcc
>> cubic
>>
>>
>> chandrika yadav k
>>
>>
>> ___
>> The Quantum ESPRESSO community stands by the Ukrainian
>> people and expresses its concerns about the devastating
>> effects that the Russian military offensive has on their
>> country and on the free and peaceful scientific, cultural,
>> and economic cooperation amongst peoples
>> ___
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>> users mailing list users@lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
> ___
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> ___
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users@lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
> —
> Stefano Baroni - Trieste —  http://stefano.baroni.me
>
>
>
>
> ___
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the 

Re: [QE-users] Simple cubic to fcc cubic

[Stefano Baroni]

Thank you Giovanni. May I suggest that in this and other similar cases help 
from the Quantum ESPRESSO Community is properly acknowledged in any work 
(thesis, paper, report) that has benefited from it? Thanks — Stefano


On 27 Feb 2024, at 11:36, Giovanni Cantele  wrote:

Let us suppose that we have a fcc crystal, with one atom per cell, at (0,0,0), 
for the sake of simplicity.

The unit cell sides are in the form (a/2,a/2,0) (a=side of the cubic cell), 
with unit cell volume a^3 / 4.

Now, let us move from fcc to sc unit cell.
Each of the 8 atoms at the corners is shared by 8 cubic cells, and thus we 
should consider only one of these atoms.
On the other hand, atoms at the center of the cube faces are shared by two unit 
cells, and count as 1/2. Since we have
6 faces, 3 out of these 6 atoms must be considered.
As a result, the sc unit cell will contain 4 atoms and a volume 4 times larger, 
a^3 as you would expect.

To go back from sc to fcc you should therefore keep 1/4 of your atoms, because 
those that are associated to the centers of three faces,
that should be explicitly considered in sc, now become equivalent (that is, 
connected by a lattice vector) to other atoms in fcc.

The code correctly finds overlapped atoms, e.g. in the example of one atom per 
unit cell, in sc you would have (0,0,0), (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2)
and the last three in fcc are obtained from (0,0,0) after a lattice translation 
by (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2), respectively.

Giovanni

--

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cant...@spin.cnr.it
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno mar 27 feb 2024 alle ore 11:14 Ms. Chandrika K. via users 
mailto:users@lists.quantum-espresso.org>> ha 
scritto:
Need help in understanding

  1.  I am currently working on Co3O4 structure,from literature it is very 
evident that it belongs to space group Fd3m(cubic fcc).
  2.
I have referred to Co3O4 Fd3m cubic structure from materials project it is 
represented as simple cubic structure but Fd3m space group refers to cubic fcc.
  3.
As it is simple cubic ibrav =1,when i change ibrav =2(cubic fcc) i am getting 
warning message
"WARNING: Atom 381 and atom 444 are very close !!!   Atom 444 deleted !!!"
ATOMIC_POSITIONS (angstrom)

I would like to know how to change the structure from simple cubic to fcc cubic


chandrika yadav k


___
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
___
Quantum ESPRESSO is supported by MaX 
(www.max-centre.eu)
users mailing list 
users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
___
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
___
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users

—
Stefano Baroni - Trieste —  http://stefano.baroni.me




___
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
___
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
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Re: [QE-users] Simple cubic to fcc cubic

[Giovanni Cantele]

Let us suppose that we have a fcc crystal, with one atom per cell, at
(0,0,0), for the sake of simplicity.

The unit cell sides are in the form (a/2,a/2,0) (a=side of the cubic cell),
with unit cell volume a^3 / 4.

Now, let us move from fcc to sc unit cell.
Each of the 8 atoms at the corners is shared by 8 cubic cells, and thus we
should consider only one of these atoms.
On the other hand, atoms at the center of the cube faces are shared by two
unit cells, and count as 1/2. Since we have
6 faces, 3 out of these 6 atoms must be considered.
As a result, the sc unit cell will contain 4 atoms and a volume 4 times
larger, a^3 as you would expect.

To go back from sc to fcc you should therefore keep 1/4 of your atoms,
because those that are associated to the centers of three faces,
that should be explicitly considered in sc, now become equivalent (that is,
connected by a lattice vector) to other atoms in fcc.

The code correctly finds overlapped atoms, e.g. in the example of one atom
per unit cell, in sc you would have (0,0,0), (a/2,a/2,0), (a/2,0,a/2),
(0,a/2,a/2)
and the last three in fcc are obtained from (0,0,0) after a lattice
translation by (a/2,a/2,0), (a/2,0,a/2), (0,a/2,a/2), respectively.

Giovanni

-- 

Giovanni Cantele, PhD
CNR-SPIN
c/o Dipartimento di Fisica
Universita' di Napoli "Federico II"
Complesso Universitario M. S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
e-mail: giovanni.cant...@spin.cnr.it 
Phone: +39 081 676910
Skype contact: giocan74

ResearcherID: http://www.researcherid.com/rid/A-1951-2009
Web page: https://sites.google.com/view/giovanni-cantele/home


Il giorno mar 27 feb 2024 alle ore 11:14 Ms. Chandrika K. via users <
users@lists.quantum-espresso.org> ha scritto:

> Need help in understanding
>
>1. I am currently working on Co3O4 structure,from literature it is
>very evident that it belongs to space group Fd3m(cubic fcc).
>2. I have referred to Co3O4 Fd3m cubic structure from materials
>project it is represented as simple cubic structure but Fd3m space group
>refers to cubic fcc.
>3. As it is simple cubic ibrav =1,when i change ibrav =2(cubic fcc) i
>am getting warning message
>"WARNING: Atom 381 and atom 444 are very close !!!   Atom 444 deleted
>!!!"
>ATOMIC_POSITIONS (angstrom)
>
> I would like to know how to change the structure from simple cubic to fcc
> cubic
>
>
> chandrika yadav k
>
>
> ___
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> ___
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users@lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
___
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
___
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users

Re: [QE-users] Simple cubic to fcc cubic

[Ramesh Kumar Kamadurai via users]

Dear Chandrika
You cannot change ibrav without changing the atom positions. To change the
structure from simple cubic to face-centered cubic (FCC), you need to make
sure that the atomic positions are arranged in a manner consistent with the
FCC crystal structure. The FCC structure has atoms located at the corners
of the unit cell as well as at the centers of each face.

Best regards,

K. Ramesh Kumar

 Assistant Professor

Gandhi Institute of Technology and Management,

 Phone: +91 9895637981, +1 6782419790

Email: kraames...@gmail.com rkama...@gitam.edu

On Tue, Feb 27, 2024 at 3:45 PM Ms. Chandrika K. via users <
users@lists.quantum-espresso.org> wrote:

> Need help in understanding
>
>1. I am currently working on Co3O4 structure,from literature it is
>very evident that it belongs to space group Fd3m(cubic fcc).
>2. I have referred to Co3O4 Fd3m cubic structure from materials
>project it is represented as simple cubic structure but Fd3m space group
>refers to cubic fcc.
>3. As it is simple cubic ibrav =1,when i change ibrav =2(cubic fcc) i
>am getting warning message
>"WARNING: Atom 381 and atom 444 are very close !!!   Atom 444 deleted
>!!!"
>ATOMIC_POSITIONS (angstrom)
>
> I would like to know how to change the structure from simple cubic to fcc
> cubic
>
>
> chandrika yadav k
>
>
> ___
> The Quantum ESPRESSO community stands by the Ukrainian
> people and expresses its concerns about the devastating
> effects that the Russian military offensive has on their
> country and on the free and peaceful scientific, cultural,
> and economic cooperation amongst peoples
> ___
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users@lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
>
___
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
___
Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users