Dear Michele,

it depends a bit on what you need to compute.

OPT 1

yambo kerr is able to directly compute the off-diagonal matrix elements of the dielectric tensor.

But i is limited to the xy plane. It works as follow.

(i) prepare the input file for a calculation in eh space (yambo -o b) using yambo_kerr in place of yambo

(ii) uncomment the EvalKerr flag

(iii) specify the direction "i" along which you want to compute the dielectric function. It must lie in the xy plane

For "i=x"

- Code: Select all
`% BLongDir`

1.000000 | 0.000000 | 0.000000 | # [BSS] [cc] Electric Field

%

yambo_kerr will give you in output eps_ii and eps_ij where "j" is the direction rotated by 90 degree (in the xy plane) compared to i.

Accordingly "i=x" then "j=y".

OPT 2

Alternatively you can do six standard calculations with yambo specifying each time a different direction and then reconstruct the whole dielectric tensor.

Yo will need (1,1,0), (1,0,1), (1,0,0), (0,1,1), (0,1,0) and (0,0,1). There are relations you can find in the literature.

Again the relevant variable is

- Code: Select all
`% BLongDir`

1.000000 | 0.000000 | 0.000000 | # [BSS] [cc] Electric Field

%

In this second case you will obtain only the symmetric part of the off diagonal elements, while in the first there will be an eventual contribution from the anti-symmetric part in case it exist in your system (for example in presence of a magnetizaton and SOC or of an external magnetic field)

Best,

D.