chiroptical properties of periodic systems

Dear Manuel,

many thanks for the info.
Chiroptical properties are accessible within the present code only via suitable post-treatment of Linear Response TD DFT which is implemented for molecular systems. We only have treatment for LDA functionals at present.

Similar treatments might work for periodic systems, although for calculations at gamma point only.

We are at present actively working on the topic of extending the functionalities (e.g. beyond LDA functionals) and to include the same treatment in the context of O(N) calculations. Therefore, should you have any specific need/interest to pursue the discussion, we might interact on the topic to coordinate development efforts.

Many thanks for the interest

Luigi

Dear Luigi

thanks for your kind reply

I am particularly interested in metal surfaces, which require sampling in
k-space for optical properties, including chiroptical ones
Certainly a TDDFT formalism would be suitable, and TDLDA seems to be very
appropriate for plasmons (surface plasmons)

Having said that, I am not aware of any TDDFT formalism for periodic
systems that includes chiroptical properties, ie you need to split the beam,
and probably the most intuitive approach would include a vector potential
(plus/minus) formalism, therefore based on TD-currentDFT

I think the chiroptical methodology would need to formulate all possible
microscopic susceptibilities, including that responsible for orbital
magnetisation,
which would require to start by a full current-DFT of magnetism in the
ground state

At this point, I am starting to get really lost, in the sense, that things
like CDFT for magnetism seem to appear for a long time in the literature as
unfinished business...

Sorry, just trying to give you my current point of view on the subject, not
to be negative

regards

Manuel
PS do you happen to have any reference on the actual implementation of
LR-TDDFT and post-treatment for chiroptical properties of molecules?

On 28 April 2017 at 09:53, Luigi Genovese <
<email address hidden>> wrote:

> Your question #629894 on BigDFT changed:
> https://answers.launchpad.net/bigdft/+question/629894
>
> Status: Open => Answered
>
> Luigi Genovese proposed the following answer:
> Dear Manuel,
>
> many thanks for the info.
> Chiroptical properties are accessible within the present code only via
> suitable post-treatment of Linear Response TD DFT which is implemented for
> molecular systems. We only have treatment for LDA functionals at present.
>
> Similar treatments might work for periodic systems, although for
> calculations at gamma point only.
>
> We are at present actively working on the topic of extending the
> functionalities (e.g. beyond LDA functionals) and to include the same
> treatment in the context of O(N) calculations. Therefore, should you
> have any specific need/interest to pursue the discussion, we might
> interact on the topic to coordinate development efforts.
>
> Many thanks for the interest
>
> Luigi
>
> --
> If this answers your question, please go to the following page to let us
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Hi Manuel,

many thanks for sharing these interesting impressions with us.
In the paper Chem. Phys, Vol. 402, p. 29 (2012) you may found the main description on how the LR-TDDFT is implemented in BigDFT code. Here just absorption spectra are investigated, for chiroptical properties in molecules as I said one should postprocess the information coming out of that, but nothing has been done on this topic so far.

CDFT computation in BigDFT are possible (see our recent literature on fragment approach, JCTC and JCP papers in 2015-6), but their suitablity should be considered on a case-by-case scenario, also with respect to potential convergence issues that might arise, especially for magnetic systems.

Topics like this are indeed very challenging and still much needs to be done at the development level. Optimistically speaking this makes room for new opportunities.

Do not hesitate to contact us should you feel this is appropriate
Many thanks

Luigi