Fragment-Based Restricted Active Space Configuration Interaction with Second-Order Corrections Embedded in Periodic...

Area of Science:

• Computational chemistry
• Solid-state physics
• Quantum mechanics

Background:

• Accurately calculating electronic structures of localized, strongly correlated features in periodic systems (crystals, surfaces) is computationally challenging.
• Existing methods may struggle with the complexity of these localized electronic interactions within extended periodic environments.

Purpose of the Study:

• To present a novel computational scheme for electronic structure calculations on fragments of periodic systems.
• To enable accurate modeling of localized strongly correlated electronic features in crystals and surfaces.

Main Methods:

• Developed a computational scheme combining restricted-active-space configuration interaction (RASCI) with second-order perturbation theory (RASCI-PT2).
• Implemented the scheme by embedding a periodic system fragment within a periodic Hartree-Fock (HF) wave function.
• Utilized an interface between the Cryscor and Q-Chem computational chemistry codes.

Main Results:

• The embedded RASCI and RASCI-PT2 methods were evaluated using dissociation of a fluorine atom from a LiF surface and a fluorinated graphane layer.
• The computational scheme successfully produced well-behaved potential energy surfaces for these systems.
• Accurate dissociation energies were obtained, validating the performance of the embedding method.

Conclusions:

• The presented computational scheme provides a robust method for studying localized strongly correlated electronic structures in periodic materials.
• The integration of RASCI/RASCI-PT2 with periodic HF embedding offers a powerful tool for materials science and condensed matter physics.
• This approach enables reliable calculations of electronic properties and reaction pathways in complex crystalline and surface systems.