[Pw_forum] the high symmetry line of bcc phonon dispersion calculated by pw4.1.2

[Ngoc Linh Nguyen]

Wei Zhou wrote:
> hello all, recently I calculated the phonon of  bcc sodium using 
> pw4.1.2, when I plot the phonon dispersion along high symmtry ,I meet 
> a problem;
> for bcc structure ,there are four high symmetry points in crystall 
> coordinations : 
> *G:(0,0,0)    H**(1/2,-1/2,1/2 )  P:(1/4,1/4,1/4)   N: (0,0,1/2 )*
I don't understand about G(0,0,0); it should be Gama point ???
> **and the pwscf give the following bcc basis
>  crystal axes: (cart. coord. in units of a_0)
>                a(1) = (  0.500000  0.500000  0.500000 )
>                a(2) = ( -0.500000  0.500000  0.500000 )
>                a(3) = ( -0.500000 -0.500000  0.500000 )
> reciprocal axes: (cart. coord. in units 2 pi/a_0)
>                b(1) = (  1.000000  0.000000  1.000000 )
>                b(2) = ( -1.000000  1.000000  0.000000 )
>                b(3) = (  0.000000 -1.000000  1.000000 )
> and I turn the high symmetry points into 2 pi/a units using 
> pwscf ,then the four high symmetry points became :
> * G :(0,0,0) ,H* *( 1.00  -1.00,1.00), P(0.00,0.00, 0.50),N(0.00, 
> -0.50, 0.50)*
>  I plot the phonon  dispersion along the high 
> symmetry *H-P-G-H-N-P-N-G, *the results is obivously wrong, which 
> differ the results from others
How did you find the intermediate points in the path between the high 
symmetry points? I suggest to use xcrysden tool to visualize the 
primitive Brillouin zone of bcc lattice, and estimate the exact values 
of the special points and the path between them.
> I am sure the phonon calculations does not have problem , the problem 
> is to how to get the correct the symmetry lines.
>  and I also found if I use the following high symmetry points 
> directly ,then the results is OK
> * G :(0,0,0) ,H* *( 0.00  1.00,0.00), P(0.5,0.5, 0.50),N(0.5, 0.5, 0.00)*
for sure, the calculation should be right because they are the high 
symmetry points.
> then I feel puzzled, would some one give some idea about this?

> any help will be appreciated
>
> -- 
> ZhouDawei
> JiLin Universiyt ,ChangChun ,China
> zdw2000 at gmail.com <mailto:zdw2000 at gmail.com>
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