[Phonopy-users] The sign of force_constant

[xirainbow <nkx...@gm...>]

Dear Professor Atz Togo:
                 I notice that the value in file "FORCE-CONSTANTS" is
 (-1)*("SECOND DERIVATIVES" in OUTCAR of VASP).
                 Is force_constant= (-1)*(SECOND DERIVATIVES of Energy over
displacements) ?

Thanks in advance:)


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Hui Wang
School of physics, Fudan University, Shanghai, China