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Hi, all,

I have this question how to calculate the static (zero-frequency) polarizability of a molecule. My thinking is that I can derive the polarizability from the dielectric constant of the molecule in a box. I simply do a test of oxygen molecule in a 20*20*20 (in angstrom^3) box. I choose the PEAD method and add a finite field and see the response. However, VASP stops due to an error:

EDWAV: internal error, the gradient is not orthogonal

I am not sure what causes this error? any help?

Thanks

I'm not sure what causes your error, but did you define the DIPOL-tag?

I'm not familiar with the PEAD method. However, one way to calculate the polarizability of a molecule is to apply an electric field to the system by the efield and idipol tags. Then calculate the polarizability tensor of the molecule by taking the second derivatives of the total energy with respect to the applied electric field.

how to derive the polarizability from the dielectric constant of the molecule in a box? Thx