Got a negative phonon frequency

[shaoziji]

Dear all,
I calculated the phonon frequency and the elph of my system with the input of teph_5.in with abinit, I used 40 Ha ecut and 40 40 40 kpoints and the phonon frequency of the ddb part (tolvr = 1.0 e-18) is positive but when calculating the gkk part (nstep = 1, tolwr = 1.0 d-22), the phonon frequency of the OUTPUT files are negetive about 600 cm-1. Is that mean that my parameters are still rough? Will the negative frequency of gkk part influence the next calculation of anaddb ?

Thanks
Shaoziji

[mverstra]

Not enough details about your calculation (read the nettiquette!!!), but on the face of it it looks ok: the nstep 1 calculation should only provide the matrix elements. The energy derivatives are certainly not converged with nstep 1 and the DDB should be obtained from a full scf DFPT calculation.