New compact density matrix averaged ANO basis sets for relativistic calculations

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Relativistic Quantum Mechanics

Background:

• Relativistic effects are crucial in quantum chemical calculations.
• Standard relativistic basis sets like ANO-RCC are computationally expensive for large systems.
• Basis set contraction can lead to significant errors in relativistic calculations.

Purpose of the Study:

• Introduce a new, compact relativistic basis set, ANO-eXtra Small (XS), for elements H-Ca.
• Reduce computational costs for relativistic quantum chemical calculations.
• Enable accurate calculations for larger molecular systems.

Main Methods:

• Development of the ANO-XS basis set with approximately half the primitive basis functions of ANO-RCC.
• Application of ANO-XS in combination with Cholesky decomposition for integral calculations.
• Validation through CASPT2 calculations on an Ir(C3H4N)3 complex.

Main Results:

• ANO-XS basis set significantly reduces computational expense.
• Molecular properties like bond lengths and excitation energies are predicted with reasonable accuracy compared to ANO-RCC.
• Hybrid calculations using ANO-XS and ANO-RCC for different regions of large systems show minor differences in results.

Conclusions:

• The ANO-XS basis set offers a computationally efficient alternative for relativistic quantum chemistry.
• It enables accurate calculations for large systems by allowing for a balance of accuracy and cost.
• This development makes advanced relativistic calculations more accessible for complex molecular studies.