Calculation of local excitations in large systems by embedding wave-function theory in density-functional theory

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Calculating local excitation energies in large systems using wave-function theory (WFT) is computationally demanding.
• Accurately describing the influence of the environment on these excitations is crucial for many chemical and physical phenomena.

Purpose of the Study:

• To develop a simple and efficient embedding scheme for WFT calculations of local excitation energies in large systems.
• To incorporate environmental effects into WFT calculations using density-functional theory (DFT).

Main Methods:

• Implementation of a WFT-in-DFT embedding procedure using ADF, Dalton, and DIRAC codes.
• Treatment of the embedded subsystem with coupled cluster methods.
• Utilizing an embedding potential derived from DFT to represent the environment.

Main Results:

• The developed scheme effectively incorporates environmental effects in calculations of the solvatochromic shift of acetone in water.
• Accurate modeling of the f-f spectrum of NpO22+ in a Cs2UO2Cl4 crystal was achieved.
• The scheme accurately models interactions of ligands with actinyl species, such as equatorial Cl- ligands in NpO2Cl42-, at reduced computational cost compared to full WFT calculations.

Conclusions:

• The WFT-in-DFT embedding scheme provides an accurate and computationally efficient method for studying local excitations in large systems.
• This approach enables reliable modeling of environmental influences and ligand interactions in complex chemical species.
• The method opens new possibilities for high-accuracy, cost-effective simulations of actinyl complexes and other challenging systems.