Time-dependent density-functional theory in the projector augmented-wave method.

Area of Science:

• Computational chemistry
• Quantum mechanics
• Materials science

Background:

• Accurate simulation of electronic excited states is crucial for understanding molecular properties and reactions.
• Time-dependent density-functional theory (TD-DFT) offers a computationally efficient approach to study excited states.

Purpose of the Study:

• To implement and compare two distinct formalisms of TD-DFT: linear-response and time-propagation.
• To validate the accuracy and assess the convergence properties of both methods.
• To demonstrate their utility in calculating spectroscopic properties and excited state dynamics.

Main Methods:

• Implementation of TD-DFT in both linear-response (LR) and time-propagation (TP) formalisms.
• Utilizing the projector augmented-wave (PAW) method within real-space grids for accurate electronic structure calculations.
• Comparison of LR-TD-DFT and TP-TD-DFT in the linear-response regime.

Main Results:

• Perfect agreement was found between LR-TD-DFT and TP-TD-DFT for calculated photoabsorption spectra.
• The study discusses the relative strengths, weaknesses, and convergence behavior of both TD-DFT formalisms.
• Successful application in calculating excitation energies, excited state potential surfaces, and nonlinear emission spectra.

Conclusions:

• The implemented TD-DFT methods, using real-space grids and PAW, provide accurate results for electronic excitation phenomena.
• Both LR and TP formalisms are valuable tools, with specific advantages for different types of calculations.
• These methods offer a robust framework for investigating excited-state properties of atoms and molecules.