Dear Francisco, 
so your AFM structure is of CuAu type. This is fine but of course 
this is not the only AFM structure possible (and I don't know whether it is 
realistic at all, but this of course depends on your objectives). 
Now, if you want the q-path to be the same in your two settings, 
you should consider that the second one is rotated by 45 degrees. 
That is, if you choose the Gamma->X direction || [010] in the first setting 
it must be || [110] in the second setting, with the lattice vectors you use. 
Otherwise define the lattice vectors as [1/2 -1/2 0], [1/2 1/2 0], [0 0 1] 
with the same lattice parameter as in the first setting 
and enjoy the same coordinates of q points (cartesian, in terms of pi/a) 
in both settings. 

Best regards 

Andrei 

----- Le 31 Déc 22, à 0:24, garcia ff 000 <garcia.ff....@gmail.com> a écrit : 

> Dear Prof. Postnikov,

> Many thanks and appreciation for your response. I believe I found a solution 
> to
> my problem but I want to run it by you.

> First, an FCC cell with 2 unique atoms is equivalent to a tetragonal cell 
> (this
> is the smallest unit cell to model antiferromagnetism).

> Using the website [ 
> https://urldefense.com/v3/__https://www.materialscloud.org/work/tools/seekpath__;!!D9dNQwwGXtA!VCzh9W4S1t5nhfeK_65w_ZsZpJauei8vdCoYcoysbxbXQ6kbxNBuSTzR-LciHx145nkwK_JGfqplTyD_aZeQ8icIeWJtZ4jCPg$
>   |
> https://urldefense.com/v3/__https://www.materialscloud.org/work/tools/seekpath__;!!D9dNQwwGXtA!VCzh9W4S1t5nhfeK_65w_ZsZpJauei8vdCoYcoysbxbXQ6kbxNBuSTzR-LciHx145nkwK_JGfqplTyD_aZeQ8icIeWJtZ4jCPg$
>   ] , the high symmetry points
> in the Brillouin zone are as follows (each set of points is scaled by the
> corresponding pi/a):

> Standard FCC primitive cell: Gamma (0,0,0), X(0,2,0), K(1.5,1.5,0), W(1,2,0),
> L(1,1,1)

> 2-atom tetragonal cell: Gamma(0,0,0), X(0,1,0), M(1,1,0), R(0,1,0.707107),
> A(1,1,0.707107), Z(0,0,0.707107).

> With this information, I believe the two Vibra inputs below, one for the
> primitive FCC cell and the other for 2-atom tetragonal cell, are formally
> equivalent (the last two k-points in each case, i.e. L and M, is what I'm a 
> bit
> unsure about).

> Thank you very much for your kindness & happy holidays.

> (A) Primitive FCC cell:

> NumberOfAtoms 1

> #Lattice parameters
> LatticeConstant 3.47 Ang
> %block LatticeVectors
> 0.500000 0.500000 0.000000
> 0.500000 0.000000 0.500000
> 0.000000 0.500000 0.500000
> %endblock LatticeVectors

> #Atomic positions
> AtomicCoordinatesFormat Fractional
> %block AtomicCoordinatesAndAtomicSpecies
> 0.000000 0.000000 0.000000 1 54.938
> %endblock AtomicCoordinatesAndAtomicSpecies

> #High symmetry Brillouin zones points scaled by pi/a: Gamma (0,0,0), X(0,2,0),
> K(1.5,1.5,0), W(1,2,0), L(1,1,1)

> BandLinesScale pi/a
> %block BandLines
> 1 0.000 0.000 0.000 \Gamma
> 30 0.000 2.000 0.000 X
> 30 2.000 2.000 2.000 \Gamma
> 30 1.000 1.000 1.000 L
> %endblock BandLines

> (B) 2-atom tetragonal cell to model antiferromagnetism (this is double the
> volume of the FCC primitive cell)

> NumberOfAtoms 2

> #Lattice parameters
> LatticeConstant 2.453660531 Ang #[this is the FCC lattice constant divided by
> sqrt(2)]
> %block LatticeVectors
> 1.000000 0.000000 0.000000
> 0.000000 1.000000 0.000000
> 0.000000 0.000000 1.414213562
> %endblock LatticeVectors

> #Atomic positions
> AtomicCoordinatesFormat Fractional
> %block AtomicCoordinatesAndAtomicSpecies
> 0.000000 0.000000 0.000000 1 54.938
> 0.500000 0.500000 0.500000 1 54.938
> %endblock AtomicCoordinatesAndAtomicSpecies

> #High symmetry Brillouin zones points scaled by pi/a: Gamma(0,0,0), X(0,1,0),
> M(1,1,0), R(0,1,0.707107), A(1,1,0.707107), Z(0,0,0.707107)

> BandLinesScale pi/a
> %block BandLines
> 1 0.000 0.000 0.000 \Gamma
> 30 0.000 1.000 0.000 X
> 30 1.000 1.000 1.000 \Gamma
> 30 2.000 2.000 2.000 M
> %endblock BandLines

> On Thu, Dec 29, 2022 at 3:34 PM Andrei Postnikov < [
> mailto:andrei.postni...@univ-lorraine.fr | andrei.postni...@univ-lorraine.fr ]
> > wrote:

>> Dear Francisco,
>> it is difficult to give a useful advice on the basis of very limited 
>> information
>> you provide,
>> but my impression is that your problems are not obviously related with Vibra.
>> Some questions:
>> 1. What (magnetic) structure are you modelling? How comes you have four atoms
>> per AFM unit cell?
>> Can there be two?
>> 2. Is electronic structure (and band dispersions) correct, prior to any 
>> phonons?
>> 3. What means "incorrect phonon dispersion"? Do you have problems with
>> crystallography /
>> choosing the q-path, or is your calculation basically wrong?
>> 4. With 4 atoms as you use it so far, the Gamma phonon calculation would 
>> yield
>> 9 modes, which would map genuine zone-center and zone-boundary modes.
>> Do they come out reasonably?

>> To your problem:
>> "B asically I want to alter the band lines in input 2 so that they are
>> equivalent to the band lines in input 1" -
>> you have
>> BandLinesScale pi/a
>> in both inputs, the same lattice parameter, and the same definition of path.
>> So if everything is correctly read, you must get the same Cartesian q-path in
>> both cases.
>> Either this is not so and there is something wrong with the input,
>> or the paths are identical but your problem is elsewhere.

>> Best regards

>> Andrei

>> ----- Le 29 Déc 22, à 0:40, garcia ff 000 < [ mailto:garcia.ff....@gmail.com 
>> |
>> garcia.ff....@gmail.com ] > a écrit :

>>> Dear Users,

>>> I have appended 2 Vibra inputs below for computing the phonon dispersion 
>>> for FCC
>>> Mn.

>>> Input 1 works fine as it gives the expected band shapes for the dispersion 
>>> (but
>>> the frequencies are off). The main issue with input 1 is that it is not
>>> suitable for antiferromagnetic calculations since there is only one Mn atom 
>>> in
>>> the primitive cell.

>>> This led me to consider input 2, which has 4 atoms in the unit cell and can 
>>> be
>>> used for antiferromagnetic calculations. The issue with input 2 is that the
>>> bandlines yield an incorrect phonon dispersion. This is what I need your 
>>> help
>>> on. Basically I want to alter the band lines in input 2 so that they are
>>> equivalent to the band lines in input 1.

>>> Any assistance with this, especially from the Vibra authors, would be 
>>> greatly
>>> appreciated.

>>> Thank you very much for your kind assistance and God Bless!

>>> Francisco

>>> #INPUT 1 (1 atom in the FCC primitive cell; 125 atoms in Supercell)
>>> SystemName fccMn_1
>>> SystemLabel fccMn_1
>>> NumberOfAtoms 1
>>> LatticeConstant 3.47 Ang
>>> %block LatticeVectors
>>> 0.500000 0.500000 0.000000
>>> 0.500000 0.000000 0.500000
>>> 0.000000 0.500000 0.500000
>>> %endblock LatticeVectors

>>> AtomicCoordinatesFormat Fractional
>>> %block AtomicCoordinatesAndAtomicSpecies
>>> 0.000000 0.000000 0.000000 1 54.938
>>> %endblock AtomicCoordinatesAndAtomicSpecies

>>> SuperCell_1 2
>>> SuperCell_2 2
>>> SuperCell_3 2

>>> AtomicDispl 0.04 Bohr

>>> BandLinesScale pi/a
>>> %block BandLines
>>> 1 0.000 0.000 0.000 \Gamma
>>> 30 2.000 0.000 0.000 X
>>> 30 2.000 2.000 2.000 \Gamma
>>> 30 1.000 1.000 1.000 L
>>> %endblock BandLines

>>> Eigenvectors True

>>> #INPUT 2 (4 atoms in the FCC conventional cell; 108 atoms in Supercell)
>>> SystemName fccMn_4
>>> SystemLabel fccMn_4
>>> NumberOfAtoms 4
>>> LatticeConstant 3.47 Ang
>>> %block LatticeVectors
>>> 1.000000 0.000000 0.000000
>>> 0.000000 1.000000 0.000000
>>> 0.000000 0.000000 1.000000
>>> %endblock LatticeVectors

>>> AtomicCoordinatesFormat Fractional
>>> %block AtomicCoordinatesAndAtomicSpecies
>>> 0.000000 0.000000 0.000000 1 54.938
>>> 0.500000 0.500000 0.000000 1 54.938
>>> 0.500000 0.000000 0.500000 1 54.938
>>> 0.000000 0.500000 0.500000 1 54.938
>>> %endblock AtomicCoordinatesAndAtomicSpecies

>>> SuperCell_1 1
>>> SuperCell_2 1
>>> SuperCell_3 1

>>> AtomicDispl 0.04 Bohr

>>> BandLinesScale pi/a
>>> # The band lines below are incorrect.
>>> %block BandLines
>>> 1 0.000 0.000 0.000 \Gamma
>>> 30 2.000 0.000 0.000 X
>>> 30 2.000 2.000 2.000 \Gamma
>>> 30 1.000 1.000 1.000 L
>>> %endblock BandLines

>>> Eigenvectors True

>>> --
>>> SIESTA is supported by the Spanish Research Agency (AEI) and by the European
>>> H2020 MaX Centre of Excellence ( [ 
>>> https://urldefense.com/v3/__http://www.max-centre.eu/__;!!D9dNQwwGXtA!VCzh9W4S1t5nhfeK_65w_ZsZpJauei8vdCoYcoysbxbXQ6kbxNBuSTzR-LciHx145nkwK_JGfqplTyD_aZeQ8icIeWKStYeflw$
>>>   |
>>> https://urldefense.com/v3/__http://www.max-centre.eu/__;!!D9dNQwwGXtA!VCzh9W4S1t5nhfeK_65w_ZsZpJauei8vdCoYcoysbxbXQ6kbxNBuSTzR-LciHx145nkwK_JGfqplTyD_aZeQ8icIeWKStYeflw$
>>>   ] )
-- 
SIESTA is supported by the Spanish Research Agency (AEI) and by the European 
H2020 MaX Centre of Excellence (http://www.max-centre.eu/)

Responder a