On Thursday 01 September 2005 09:37, XiaoSong Du wrote: > what i can't understand is the meaning of the 4 q-points in the star. > Number of q in the star = 4 > List of q in the star: > 1 -0.250000000 -0.250000000 0.250000000 > 2 0.250000000 0.250000000 0.250000000 > 3 0.250000000 -0.250000000 -0.250000000 > 4 -0.250000000 0.250000000 -0.250000000 > In addition there is the -q list: > 1 0.250000000 0.250000000-0.250000000 > 2-0.250000000-0.250000000-0.250000000 > 3-0.250000000 0.250000000 0.250000000 > 4 0.250000000-0.250000000 0.250000000
the code uses a rather complex symmetrization, involving the response to several displacement patterns that transform into each other. As a result one gets the dynamical matrix at all the q-vectors that belong to the same star. There are 8 vectors in the star of <1/4, 1/4, 1/4> for cubic materials, and the results for -q and q are the same because of time reversal symmetry. > By the way in the example I find the inputfile of non-scf and phonon > calculation of GaAs describing k-space sampling is wrong, which > should be a 444 M_P sampling instead of the 2 point. Am I right? it is a 444 Monkhorst-Pack sampling, without displacement (the grid has to include q=0) Paolo -- Paolo Giannozzi e-mail: giannozz at nest.sns.it Scuola Normale Superiore Phone: +39/050-509876, Fax:-563513 Piazza dei Cavalieri 7 I-56126 Pisa, Italy
