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> > ------------------------------------------------------------------------ > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum >
