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/)