[Pw_forum] questions about symmetry and the elphon output

[Paolo Giannozzi]

On Oct 20, 2006, at 16:45 , Jia-An Yan wrote

>  For the same graphene system, when I use ibrav=0 with cell  
> parameters,
> I got only 8 symmetry operations( with inversion) [...] However,  
> since the graphene system is hexagonal, I rotate the coordinate  
> system and use ibrav=4 to define the system, then I got 24 sym  
> operations (with inversion). There are also six modes (with 2  
> degenerate modes) obtained. Why does the pw.x obtained different  
> symmetry for the same system?

because you did not specify option "hexagonal" to card
CELL_PARAMETERS, I guess

> Note that the order of the omega is different from the calculation  
> order
> (2 1 2 1)

irreps used for the calculation are randomly generated;
normal modes are ordered according to their frequency.
There is no reason for them to follow the same ordering.

Paolo