Neutral excitation density-functional theory: an efficient and variational first-principles method for simulating...

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Calculating electronic excitations is crucial for understanding material properties.
• Existing methods like linear-response time-dependent density functional theory (LR-TDDFT) can be computationally expensive.
• A need exists for efficient and accurate methods for electronic excitation calculations.

Purpose of the Study:

• Introduce neutral excitation density-functional theory (XDFT) as a novel computational method.
• To develop a computationally light, generally applicable, first-principles technique for neutral electronic excitations.
• To enable accurate calculation of optical gaps and electron-hole binding energies.

Main Methods:

• Generalize constrained density functional theory (DFT) to remove assumptions on electron-hole spatial confinement.
• Employ a sequence of coupled DFT calculations to find the lowest excited state of a given symmetry.
• Validate XDFT by calculating singlet and triplet excitation energies for a molecular test set.

Main Results:

• XDFT accurately calculates lowest single-particle singlet and triplet excitation energies, showing good agreement with LR-TDDFT.
• The method demonstrates capability in capturing two-electron excitations.
• Achieved computational cost and scaling comparable to standard DFT.

Conclusions:

• XDFT provides a computationally efficient and broadly applicable approach for electronic excitation calculations.
• The method makes optical gaps and electron-hole binding energies readily accessible.
• XDFT is suitable for high-throughput materials discovery and informatics due to its low computational demand and ease of automation.