CMSP Seminar (Atomistic Simulation Webinar Series): 16 March at 11:00, Dr Martina Stella

[CMSP Seminars Secretariat]

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Atomistic Simulation Webinar Series
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WEBINAR_

via Zoom



** * * Wednesday, 16 March 2022 at 11:00*** * **

Speaker:*Dr. Martina Stella *(ICTP )


Title:***Towards a systematic multi-scale method for excitations in 
molecular materials in the BigDFT code
*

Register in advance at:
https://zoom.us/meeting/register/tJYsc-6vqjIvE93WmBUS1eReomlWFjskhyvv
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_Abstract_:

Understanding excited states and their relaxation plays a critical role 
in spectroscopy as well as in improving the performance of technological 
devices. For instance, being able to predict where excited states lie 
for molecules embedded in crystals can be crucial for guiding 
experimentalists in locating excitation sources. From a technological 
perspective an interesting example is thermally activated delayed 
fluorescence (TADF). It represents a promising mechanism for designing 
the next generation of OLED (Organic Light Emitting Diodes) materials 
being fully organic and less environmental harmful than previous generation.

TADF emission is based on inverse inter-system crossing from triplet 
state to singlet states. These excitations have shown to exhibit an 
intricate mixture of charge-transfer and local nature. Modelling TADF 
(e.g to identify the best performing material) as well as locating 
excited states, thus, requires a methodology able to provide high 
accuracy while explicitly including environmental effects. However, 
developing a versatile theoretical approach for the characterisation of 
excitations can be challenging due to the complexity of the methods 
available and the variety of sources of error associated with them.

We are developing a multi-scale approach within the BigDFT code where we 
combine the needed accuracy with the ability of treating big systems, 
which would allow one to go beyond implicit models. BigDFT is designed 
to run on parallel architectures and can treat large systems while 
ensuring high, controllable precision.

As a first step towards a robust methodology, we assess the performance 
of a novel promising constrained-DFT (T-CDFT) approach we recently 
developed while I was at Imperial College London and compare the results 
with standard methods (e.g. TDDFT) and simulation conditions. Such 
investigation is conducted on a diverse set of molecules (e.g. TADFs, 
acenes) in order to cover various classes of excitations. This phase is 
carried out by also developing portable jupyter-notebooks for the 
analysis of excitations.

1) Daubechies wavelets for linear scaling density functional theory,S 
Mohr, LE Ratcliff, P Boulanger, L Genovese - The Journal of chemical 
physics, 2014, 2)Fragment approach to constrained density functional 
theory calculations using Daubechies wavelets, LE Ratcliff, L Genovese, 
S Mohr, T Deutsch - The Journal of chemical physics, 2015, 
3)Transition-based Constrained DFT for the robust and reliable treatment 
of excitations in molecular systems, M Stell, K Thapa, L Genovese and LE 
Ratcliff, JCTC, submitted , 2021.




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CMSP Seminars support:OnlineCMSP at ictp.it  

CMSP, Condensed Matter & Statistical Physics Section
http://www.ictp.it/research/cmsp.aspx

The Abdus Salam International Centre for Theoretical Physics
https://www.ictp.it/

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