[Pw_forum] questions about symmetry and the elphon output

[Jia-An Yan]

Thanks, Paolo, I get it.

Jia-An

>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
>
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