State-Specific Density Functionals for Excited States via a Density-Driven Correlation Model

Area of Science:

• Quantum Chemistry
• Computational Physics
• Materials Science

Background:

• Standard density-functional approximations often fail to accurately describe excited states.
• Density-driven correlations (ddc's) are crucial for understanding excited states but are missed by ground-state methods.

Purpose of the Study:

• To develop a first-principles strategy for accurate excited state approximations.
• To incorporate density-driven correlations (ddc's) into ensemble density functionals.
• To address limitations of current density-functional theory (DFT) for excited states.

Main Methods:

• Utilizing ensemble density functionals to model excited states.
• Exploiting the low-density limit of electrons in excited states to model ddc's.
• Implementing a difference in self-consistent field (ΔSCF) approach for calculations.

Main Results:

• A proof-of-concept excited state approximation was developed.
• The new approximation resolves failures in describing double excitations, charge transfer excitations, and piecewise linearity.
• The method demonstrates impressive performance for modeling excited states.

Conclusions:

• The proposed strategy represents a significant advancement in modeling neutral and charged excitations.
• This approach offers a pathway toward unified and accurate excited-state calculations.
• The method effectively captures density-driven correlations essential for excited states.