ionization in RT-TDDFT

[Carles]

Dear all,

I am doing some tests using strong laser pulses with rt-TDDFT and I don't obtain the ionization rate of the molecule that I would expect. Do you know any examples of ionization calculations performed with rt-TDDFT that could help me?

Thank you, and best regards,

Carles

[niri....@gmail.com]

Hi Carles,

I have never tried calculating ionization rates with RT-TDDFT, so I don't know what to expect. 

However, I suspect you will need a higher level of theory to get this accurately. Before you do that, you could try calculating the ionization rates with a range-separated exchange-correlation functional (with full long-range correction) to take care of the asymptotic behaviour of the functional. Please see the DFT section of our manual for the keywords for these functionals 

Can you also post some details of your calculations and the experimental numbers/the numbers you expect ? 

Thanks.

Best regards,

-Niri

Niri Govind

PNNL

niri....@pnnl.gov

[Vijay Mocherla]

Hello,

I have been trying to run some molecular ionization simulations and calculate the ionization rates using RT-TDDFT. 

The only references I can think of are some papers by Ken Lopata (for example, see this paper). They've tuned some range-separated hybrids specifically for SFI calculations, though this with a CW laser field, not an actual few cycle CEP stablised pulse that's more commonly used in strong-field experiments like HHG or attoclock.

Can someone please point me to the place where I can find keywords for LC-PBE* or the other tuned range-separated functionals?  Or does the composition of the xc functional have to be mixed(from functionals given here), the way its done for cam-b3lyp in some of the examples in documentation.

Thanks.

Vijay

[Carles]

Hello Vijay,

I am glad there is someone here working also on ionization rates with RT-TDDFT!

I can only add that I cannot get any result from the CAP implemented in NWChem 7.0.2.

For instance, running the example given at the end of the page

https://nwchemgit.github.io/RT-TDDFT.html

I have changed several parameters, but I can't get any change on the water absorption spectrum, can you?

I wonder if the CAP is correctly implemented in NWChem 7.0.2.

Best wishes,

Carles

El dia dilluns, 2 de maig de 2022 a les 19:25:17 UTC+2, Vijay Mocherla va escriure:

[niri....@gmail.com]

Hi Vijay,

The LC-PBE* is just a variant of LC-PBE, defined on our DFT page (https://nwchemgit.github.io/Density-Functional-Theory-for-Molecules.html)

Except that the parameters have been tuned based on Koopman's theorem. Please see the following paper https://pubs.acs.org/doi/full/10.1021/ct400569s  where we describe the tuning procedure for the parameters.

Best,

-Niri

[Vijay Mocherla]

Thanks for the reference.

I somehow missed this paper, though it's been cited in the paper I had mentioned earlier in the thread.

For anyone who's still looking to tune the DFT functional see: https://nwchemgit.github.io/Density-Functional-Theory-for-Molecules.html#range-separated-functionals

  

Vijay

--------------------------------------------------------
Sai Vijay Mocherla

Junior Research Fellow,
Centre for Interdisciplinary Sciences

Tata Institute of Fundamental Research, Hyderabad

Website : vijaymocherla.github.io

Email: saivijay...@tifrh.res.in

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