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Low bandgap and donor-acceptor molecular systems as described by a hybrid functional with local range separation

Grant number: 24/02191-2
Support Opportunities:Scholarships abroad - Research Internship - Doctorate (Direct)
Effective date (Start): May 01, 2024
Effective date (End): October 31, 2024
Field of knowledge:Physical Sciences and Mathematics - Physics - Condensed Matter Physics
Principal Investigator:Thiago Branquinho de Queiroz
Grantee:Reinaldo Vieira Dantas Filho
Supervisor: Stephan Kummel
Host Institution: Centro de Ciências Naturais e Humanas (CCNH). Universidade Federal do ABC (UFABC). Ministério da Educação (Brasil). Santo André , SP, Brazil
Research place: University of Bayreuth, Germany  
Associated to the scholarship:22/03461-8 - Time-dependent density functional theory approximations for charge separation processes, BP.DD


Organic photovoltaic devices are often composed of low bandgap molecular systems forming donor-acceptor heterojunctions. The design of more efficient and durable devices is highly guided by the reliable description of their electronic and optical properties. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) are among the most used approaches to theoretically predict these properties as they provide a good balance between computational cost and accuracy. However, common approximations for the exchange-correlation (xc) energy such as semilocal functionals and global hybrids fail to describe charge transfer (CT) transitions due to various fundamental problems, that have been partially solved with the range separated hybrid (RSH) functionals. Yet, the use of a global range separating parameter in the RSH functionals also has shortcomings, since it is a system specific parameter to be tuned. To solve these shortcomings, the concept of constructing the range separating parameter as a functional of the density has been proposed by Krukau et al. [JCP 129, 124103(2008)], the local range separated hybrid (LRSH) functional. T. Aschenbrock and S.Kümmel [JCP 151, 154108 (2019)] have constructed a LRSH functional that satisfies specific exact constraints, leading to a LRSH functional that depends on two parameters (· and ³). Latter, M. Brütting, H. Bahmann and S. Kümmel [JCP 156, 104109 (2022)] showed that one can optimize these parameters as tuples to accurately describe target properties such as atomization energies and reaction barrier heights. In this project, we aim to assess the performance of this LRSH functional to describe low bangap oligomers and donor-acceptor molecular systems in comparison to the optimally-tuned RSH functional. We are also going to optimize the tuples of (·, ³) for ionization energies and frontier orbital eigenvalues. This research visit is going to be supervised by Prof. Dr. Stephan Kümmel (University of Bayreuth, Germany) and hosted in his group, a group with considerable experience in the development of density functional approximations.

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