On the geometry dependence of tuned-range separated hybrid functionals.

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Accurate excited-state properties are vital for designing novel light-absorbing and emitting molecules and materials.
• Time-dependent density functional theory (TDDFT) offers a balance of efficiency and accuracy for excited-state calculations.
• Standard TDDFT approximations struggle to accurately describe all excited states, particularly those with charge-transfer (CT) characteristics.

Purpose of the Study:

• To improve the description of excited-state properties within TDDFT, focusing on charge-transfer characteristics.
• To investigate the application of optimal tuning and triplet tuning methods for nonempirical range-separated functionals.
• To analyze the CT properties of PTZ-DBTO2 and TAT-3DBTO2, two thermally activated delayed fluorescence emitters.

Main Methods:

• Applied optimal tuning and triplet tuning methods for nonempirical definition of range-separated functionals.
• Utilized TDDFT to study excited-state properties.
• Investigated the CT properties of specific organic molecules (PTZ-DBTO2 and TAT-3DBTO2).

Main Results:

• Demonstrated the connection between optimal tuning and triplet tuning methods.
• Evaluated the performance of these tuning methods in the presence of multiple excited states with varying characters.
• Analyzed the geometry dependence of the tuning methods, crucial for developing size-consistent potential energy surfaces.

Conclusions:

• The developed nonempirical range-separated functionals offer improved excited-state descriptions in TDDFT.
• These methods provide a more accurate characterization of charge-transfer properties in complex molecules.
• The findings are relevant for the rational design of advanced materials for optical and electronic applications.