Second-Order CASSCF Algorithm with the Cholesky Decomposition of the Two-Electron Integrals.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Theoretical chemistry

Background:

• Complete Active Space Self-Consistent Field (CASSCF) calculations are crucial for accurately describing electron correlation in molecules.
• Standard CASSCF optimization methods can be computationally expensive due to the involvement of the full Hessian matrix.
• The norm-extended optimization algorithm ensures convergence but exacerbates computational costs.

Purpose of the Study:

• To implement a computationally efficient second-order CASSCF algorithm.
• To reduce the computational cost and memory requirements of CASSCF calculations.
• To enable routine calculations for larger molecular systems.

Main Methods:

• Implementation of a second-order CASSCF algorithm.
• Integration with Cholesky decomposition of two-electron repulsion integrals.
• Utilizing the norm-extended optimization strategy for guaranteed convergence.

Main Results:

• Significant reduction in computational cost and memory usage.
• Improved parallel performance of CASSCF calculations.
• Successful benchmark calculations on systems up to 3000 basis functions and 14 active orbitals.

Conclusions:

• The Cholesky-decomposed second-order CASSCF method offers a practical solution for large-scale electronic structure calculations.
• This approach makes advanced quantum chemical modeling more accessible for complex molecular systems.
• The enhanced efficiency opens new avenues for research in various fields of chemistry and materials science.