LCAO-TDDFT-k-ω: spectroscopy in the optical limit

Area of Science:

• Materials Science
• Computational Physics
• Quantum Chemistry

Background:

• Understanding optical absorption, exciton dynamics, and charge transport in low-dimensional systems is crucial for materials science.
• Existing methods for modeling optical properties of these systems are often inefficient or lack physical insight.

Purpose of the Study:

• To develop and validate a robust and efficient computational method for modeling the optical absorbance of low-dimensional macromolecular systems.
• To provide physical insight into the underlying processes of optical excitation and charge separation.

Main Methods:

• Employed a linear combination of atomic orbitals (LCAO) representation within time-dependent density functional theory (TDDFT) in reciprocal space (k) and frequency (ω) domains.
• Utilized a derivative discontinuity correction (Δx) as a scissors operator for Kohn-Sham (KS) eigenenergies.
• Applied the LCAO-TDDFT-k-ω code to 0D, 1D, 2D, and 3D systems (C60, CNTs, graphene, phosphorene, TiO2) and analyzed electron-hole spectral density.

Main Results:

• Achieved semi-quantitative agreement for photoabsorption cross-section, conductivity, and dielectric function compared to experimental data and G0W0-BSE calculations.
• Provided spatially and energetically resolved electron-hole spectral densities, offering direct physical insight into optical excitations.
• Demonstrated the reliability, applicability, efficiency, and robustness of the LCAO-TDDFT-k-ω code.

Conclusions:

• The LCAO-TDDFT-k-ω code offers a powerful tool for accurate modeling of optical properties in diverse low-dimensional materials.
• This method facilitates the computational design of macromolecular systems for advanced optoelectronic, photovoltaic, and photocatalytic applications.