[Pw_forum] Fwd: fft-check warning: sum of imaginary terms 0 .1649464E-06 in q2r.x

[Kondaiah Samudrala]

Dear all,

I am calculating Phonon dispersion of AB2 type compound under pressure up
to 150 GPa. From 0 to 90 GPa i got nice phonon dispersions, where as I
found

*fft-check warning: sum of imaginary terms= .1649464E-06*

warning at 100 GPa and 110 GPa.

Even After seen the forums i put large conversion values such as
etot_conv_thr = 1.0D-8 ,
forc_conv_thr = 1.0D-5 ,
conv_thr = 1.D-10 ,
tr2_ph=1.0d-16,

I did the calculations with 120 Ry and 14X12X12 k-mesh, 4X4X4 and 6X6X6
q-mesh for phonon dispersions. My 0 to 90 GPa computed values are good in
agreement with experiments. Including this, I did not get ant imaginary
frequenciesin AB2.dyn files at 90 GPa and 100 GPa.  Here with I am
attaching My 90 GPa and 100 GPa phonon dispersions

Pls help me in this problem. Thanks in advance


with regards
S. Applakondaiah
Senior research fellow
University of Hyderabad
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