Damped (linear) response theory within the resolution-of-identity coupled cluster singles and approximate doubles...

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Coupled cluster methods are essential for accurate electronic structure calculations.
• Calculating response functions, especially for large molecules, presents significant computational challenges.
• Existing methods may struggle with storage requirements for large systems.

Purpose of the Study:

• To implement a complex solver for the resolution-of-identity coupled cluster singles and approximate doubles (RI-CC2) method.
• To enable the computation of complex response functions for damped response theory.
• To develop a computationally efficient formalism for linear and nonlinear response properties.

Main Methods:

• Implementation of a partitioned formulation for the complex solver.
• Avoidance of storing double excitation amplitudes for scalability.
• Application of the RI-CC2 method for response calculations.

Main Results:

• Successful computation of complex response functions for RI-CC2.
• Demonstrated applicability to large molecules due to efficient storage.
• Calculated one-photon absorption cross section of C60.
• Computed electronic circular dichroism of n-helicenes.
• Determined C6 dispersion coefficients for organic molecules and fullerenes.

Conclusions:

• The developed solver is a key component for damped coupled cluster response theory.
• The method is suitable for studying linear and nonlinear optical properties in resonant frequency regions.
• The implementation provides accurate results for diverse molecular systems and properties.