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["duan_semi" <abinit_duan@126.com>]

Dear abinitusers,

           I want to calculate the Proper piezoelectric constants (clamped ion and relaxed ion) of tetragonal phase of PbTiO3. I set my input files just following the example of AlAs in tutorial (the input file for RF calculation ,that for "anaddb" and the output file after using "anaddb" are the attached files). the calculation of RF is successful and the "DDB" file is gotten. After the analysis of "anaddb"  is finished, there is a warning message in the output file of "anaddb":

    "piezo9 : WARNING -
   Unstable eigenvalue detected in force constant matrix at Gamma point
   The system under calculation is physically unstable."

I think the problem maybe affect the precision and validity of   piezoelectric constants. Is what I think is right? what I should do to solve it?

Best regards,

WD Duan      

 

 

 

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Attachment: p4mm.in
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Attachment: p4mm_anaddb.in
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Attachment: p4mm_anaddb.out
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