[Pw_forum] why the ASR change the mode in the high frequency ?

[xu yuehua]

hi all :
i am calculating the phonon at Q=0, my system is one-dimension , so
strictly,there should be 4 zero-frequency. and my result is 0, 24, 31,
38cm-1,
in order to get better result, i add the  asr, and of course, the above 4
modes change to be 0cm-1, but  another mode at  high frequency,changes from
3002 to 2880cm-1,

the difference is big,   and the pwscf forum give me some information :"if
the dynamical matrix is diagonalized with program dynmat.x imposing the ASR,
[image: $ \omega$] should go much closer to 0, with all other modes
virtually unchanged"
so i am wondering, why the mode at 3002cm-1 has so much change ?

-- 
Xu Yuehua
physics Department of Nanjing university
China
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