ABINIT Discussion Forums

Dear all,

I want to calculate the dielectric tensor at an heteroepitaxial semiconductor interface (IF) GaP on Si.
But first of all, I'd like to explain my procedure:

*I run a ground state (GS) calculation of that IF, realized by a multilayer modelling (...si-layers--gap-layers--si-layers--gap-layer...) as you can see in gap-si-p2.in
*Then I run a response function calculation to get the momentum matrix (ddk) as it is described in the optic-tutorial. (see for p.in)
*finally I run an optic calculation to get the frequency dependent dielectric tensor (see for p-optic.in)

The calculation itself run without errors. But my problem is:
Actually I am interested in electronic dielectric tensor elements at this IF, that is, there must be direction-dependent tensor elements (element 11 is unequal element 22, if I consider the plane (001) to be plane of Interface). But due to the model there are 2 IF's in the unit cell, and furthermore, due to the zinkblende structure [100] directional properties of the one IF are the same as those of the [010] direction of the other interface. Therefore, differences seem to "sum up " (I hope, this bad description isn't missunderstood!!) and finally there is no difference in 11 and 22 elements of the dielectric tensor. Ideally, I would like to calculate this perturbation for just one IF, e.g. for atoms 4 to 13, but I know that is not possible.

Could anybody help me? Is there another way to calculate dielectric tensor over a frequency range for just a part of my model?

I know this sounds little awkward, but I'd appreciate any help or suggestion!

Kind regards,

Gabi

Hello, interesting problem, though I'm not sure if the dielectric constant is well defined for such a small system.

you could do a slab, introducing vacuum instead of the interface you want to remove, but then you have the response of your "IF" and 2 surfaces - you might also have to look at the response of the different surfaces for the 2 component subsystems... In some cases these things add up, but this is far from guaranteed.

Matthieu