Absorption Spectra of Solids from Periodic Equation-of-Motion Coupled-Cluster Theory

Area of Science:

• Computational materials science
• Quantum chemistry
• Solid-state physics

Background:

• Accurate prediction of optical properties is crucial for designing new materials.
• Ab initio methods provide a theoretical framework for understanding electronic excitations.

Purpose of the Study:

• To compute ab initio absorption spectra for six 3D semiconductors and insulators.
• To assess the accuracy and efficiency of Gaussian-based periodic equation-of-motion coupled-cluster theory with single and double excitations (EOM-CCSD).
• To investigate the impact of various approximations on spectral calculations.

Main Methods:

• Gaussian-based periodic equation-of-motion coupled-cluster theory with single and double excitations (EOM-CCSD).
• Efficient calculation of spectra by solving linear equations at each frequency.
• Assessment of approximations: Brillouin zone sampling, frozen orbitals, and partitioned EOM-CCSD.

Main Results:

• Calculated ab initio absorption spectra for six 3D semiconductors and insulators.
• Achieved good agreement in spectral line shapes with experimental data.
• Observed a consistent blue shift of approximately 1 eV in calculated spectra compared to experiments.
• Identified that finite-size errors do not fully explain the observed energy shift.

Conclusions:

• The EOM-CCSD method provides a reliable approach for calculating absorption spectra.
• The observed energy shift suggests the importance of unconsidered factors like vibrational effects and higher-order electron correlation (e.g., triple excitations).
• Further theoretical refinements are needed to fully reconcile calculated and experimental spectra.