Time-dependent density functional theory description of total photoabsorption cross sections

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical spectroscopy

Background:

• Accurate calculation of molecular photoabsorption cross sections is crucial for understanding light-matter interactions.
• Previous studies have established benchmarks using coupled cluster methods, but computational cost limits their application to larger systems.

Purpose of the Study:

• To apply time-dependent density functional theory (TDDFT) for calculating photoabsorption cross sections of various aromatic molecules.
• To validate TDDFT results by comparing them with established linear response coupled cluster (LRCC) methods.
• To establish TDDFT as a reliable method for photoabsorption spectroscopy.

Main Methods:

• Utilized time-dependent density functional theory (TDDFT) to compute electronic structures.
• Employed discrete electronic pseudo-spectra from L^2 basis set calculations.
• Applied an analytic continuation procedure to derive photoabsorption cross sections.
• Used ammonia as a model system for benchmarking against linear response coupled cluster (LRCC) calculations.

Main Results:

• TDDFT successfully calculated the total photoabsorption cross sections for benzene, pyridine, furan, pyrrole, thiophene, phenol, naphthalene, and anthracene.
• The study established a link between TDDFT and LRCC results, confirming TDDFT's accuracy.
• Benchmarks were successfully established for TDDFT in photoabsorption calculations.

Conclusions:

• TDDFT is a computationally efficient and accurate method for determining photoabsorption cross sections of molecules.
• The established benchmarks provide confidence in using TDDFT for future spectroscopic studies.
• This work facilitates broader applications of theoretical spectroscopy in chemistry and physics.