The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <gonze@pcpm.ucl.ac.be>]

Dear Mike,

Mike wrote:
> I conducted a response function calculation and then used IFC to analyze 
> DDB file, but I got the ERROR as follows:
> 
>   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 :
>  -1.44436452E-03 -1.44432637E-03 -1.40826927E-03 -1.00781976E-03
> 
>

Could you send the input file to IFC, as well as
some input file(s) of the corresponding ABINIS
calculation ? This is needed to see what kind of system
you have ...

Thanks,
Xavier