Frozen Natural Spinors for Cholesky Decomposition-Based Two-Component Relativistic Coupled Cluster Method

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Relativistic Quantum Chemistry

Background:

• Accurate electronic structure calculations are crucial for understanding molecular properties.
• Four-component relativistic coupled cluster (CC) methods provide high accuracy but are computationally expensive.
• Efficient implementations are needed for studying large and complex systems.

Purpose of the Study:

• To present an efficient and cost-effective implementation of the exact two-component atomic mean field (X2CAMF)-based coupled cluster (CC) method.
• To integrate frozen natural spinors (FNS) and Cholesky decomposition (CD) for reduced computational cost and memory requirements.
• To demonstrate the method's accuracy and efficiency for relativistic systems.

Main Methods:

• Exact two-component atomic mean field (X2CAMF) coupled cluster (CC) method.
• Integration of frozen natural spinors (FNS) for reduced active space.
• Application of Cholesky decomposition (CD) for efficient integral storage and transformation.
• Calculation of a medium-sized uranium complex.

Main Results:

• The FNS and CD approximation significantly reduces storage requirements without compromising accuracy.
• The developed X2CAMF-CC method achieves accuracy comparable to canonical four-component relativistic CC methods.
• The method is computationally efficient, demonstrated by calculations on a large uranium complex.

Conclusions:

• The FNS and CD-based X2CAMF-CC method offers a highly accurate and computationally feasible approach for relativistic electronic structure calculations.
• This method provides a cost-effective alternative to traditional four-component methods for complex systems.
• The implementation enables the study of larger and more intricate relativistic molecules.