[Pw_forum] uncertainty about the *.dynG file :what is "cubic" mean ? and what is the difference between *.dyn and *. matdyn file ?

[degironc]

the word "cubic" is a reminder for the code that the symmetry group of 
the crystal in a subset of the cubic one (the other option would be 
"hexagonal"). this does not means that the system is actually cubic but 
just that the symmetry operations that it satisfies should be searched 
among those of the cubic group.
.. is "cubic" the right symmetry system for your crystal ? the 
fundamental lattice vectors you get look like belonging to some 
triangular lattice...
stefano

xu yuehua wrote:
> hi all :
> In the *.dynG file ,there is "cubic" ,i don know what is meaning 
> ,because my cell is not the type as you can see my scf file
>  
> -------------------------------------dynG.FILE 
> ------------------------------
>
> Dynamical matrix file
>
>   2   15  0 38.1852405  0.0000000  0.0000000  0.0000000  0.0000000  
> 0.0000000
> cubic
>       0.866025710    0.499999470    0.000000000
>       0.000000000    0.999998940    0.000000000
>       0.000000000    0.000000000     0.143563323
>
> ------------------------------------------------------------------------scf 
> file -----------------------------------
> this is the scf output :
>
> bravais-lattice index     =            0
>      lattice parameter (a_0)   =      38.1852  a.u.
>      unit-cell volume          =    6922.4594 (a.u.)^3
>      number of atoms/cell      =           15
>      number of atomic types    =            2
>      kinetic-energy cutoff     =      29.9874  Ry
>      charge density cutoff     =     200.0000  Ry
>      convergence threshold     =      1.0E-09
>      beta                      =       0.2000
>      number of iterations used =            8  plain     mixing
>      Exchange-correlation      =  SLA  PW   PBE  PBE (1434)
>      celldm(1)=  38.185240  celldm(2)=   0.000000  celldm(3)=   0.000000
>      celldm(4)=   0.000000  celldm(5)=   0.000000  celldm(6)=   0.000000
>
>      crystal axes: (cart. coord. in units of a_0)
>                a(1) = (  0.866026  0.499999  0.000000 )
>                a(2) = (  0.000000  0.999999  0.000000 )
>                a(3) = (  0.000000  0.000000  0.143563 )
>
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> -- 
> Xu Yuehua
> physics Department of Nanjing university
> China