Spin-Scaled Range-Separated Double-Hybrid Density Functional Theory for Excited States

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Density Functional Theory (DFT) is a powerful tool for electronic structure calculations.
• Time-dependent DFT (TDDFT) extends DFT to describe electronic excitations.
• Double-hybrid (DH) functionals offer improved accuracy but can be computationally expensive.

Purpose of the Study:

• To combine range-separated (RS) double-hybrid (DH) TDDFT with spin-scaling techniques.
• To develop and evaluate spin-component-scaled (SCS) and scaled-opposite-spin (SOS) variants.
• To assess the performance of these new methods for a wide range of electronic excitations.

Main Methods:

• Implementation of spin-scaling techniques (SCS and SOS) within the RS-DH framework.
• Systematic benchmark calculations on nearly 500 electronic excitations.
• Comparison with existing prominent DH functionals and nonempirical functionals.

Main Results:

• The RS-DH ansatz demonstrates robustness across various excitation types.
• SCS variants consistently improve accuracy compared to the original RS-DH method.
• SOS variants maintain the benefits of RS-DH while reducing computational cost.
• Nonempirical functionals show balanced performance for general applications.
• Specific methods are recommended for particular types of excitations.

Conclusions:

• The developed SCS and SOS variants of RS-DH TDDFT are effective for accurate excitation energy calculations.
• These methods provide valuable insights into the performance of DH functionals.
• The study guides the selection of appropriate computational methods for specific excitation problems.