[Pw_forum] phonon at Gamma point

[Ezad Shojaee]

hi
i am trying to calculate phonon frequencies at gamma point of TiO2(anatase) 
and i have relaxed the structure enough (i think )but performing PH.X after 
scf, 2of 18 frequencies  are minus!
i want to know that what technical problem do i have? does anyone calculate 
these beore?
any suggestion will be appreciated

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