[Pw_forum] Units of Raman Tensor

[giannozz at democritos.it]

Quoting "S. Sanchez" <lcqsigi at gmail.com>:

> My question arises given the fact that the dchi/dr tensor can be obtained as
> the third order derivative of the Energy (in units of Ry or Ha) with respect
> to the atomic displacement (bohr) and two times the electric field (e/bohr).
>
> dchi/dr=d^3E/(dr*de1*de2)
> where E is the Energy; r the displacement, e1 and e2 the electric fields.

I don't have here my notes, but e^2/8\pi (e=electric field)
is an energy density, i.e. energy per unit volume, so 
dchi/dr=d^3E/(dr*de1*de2) has the dimension of r^2.

P.

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