Towards a spin-adapted coupled-cluster theory for high-spin open-shell states

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• High-spin open-shell systems present challenges in quantum chemical calculations.
• Traditional methods may not fully account for spin properties in these systems.

Purpose of the Study:

• To propose a novel spin-adapted coupled-cluster (SA-CC) scheme.
• To address the accurate quantum chemical treatment of high-spin open-shell cases.
• To evaluate the computational feasibility and accuracy of the proposed SA-CC scheme.

Main Methods:

• Development of a spin-adapted coupled-cluster (SA-CC) scheme incorporating spin constraints.
• Pilot implementation of the SA-CC scheme within the singles and doubles approximation.
• Conducting test calculations on high-spin open-shell systems.

Main Results:

• Demonstration of the computational feasibility of the proposed SA-CC scheme.
• Test calculations show the SA-CC scheme achieves accuracy comparable to traditional methods.
• The inclusion of spin constraints improves the treatment of high-spin cases.

Conclusions:

• The proposed spin-adapted coupled-cluster (SA-CC) scheme offers a viable and accurate approach for high-spin open-shell systems.
• This method provides a valuable alternative to traditional quantum chemical treatments.
• Further development and application of this SA-CC scheme are warranted.