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["Wu Rongqin" <g0203654@nus.edu.sg>]

Dear all,

I calculated the ddb file of SrTiO3 and processed it with anaddb. I hope to get the frequency dependent dielectric but it tells something like this:

( it is true a soft mode exist)

diel9 : ERROR -

  The lowest mode appears to be a "true" negative mode,

  and not an acoustic mode. This precludes the computation

  of the frequency-dependent dielectric tensor.

  Action : likely there is no action to be taken, although you,

  could try to raise your convergence parameters (ecut and k-points).

 For your information, here are the four lowest frequencies :

 -4.39601830E-04 -4.39600532E-04 -4.39600084E-04  0.00000000E+00

 

how can I get the dielectric constant epsilon_zero and IR response then?

 

I am desperate

Rongqin