Polarizable Density Embedding Coupled Cluster Method.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate modeling of chemical systems requires high-level quantum chemistry methods.
• The environment significantly influences the electronic properties of a core chemical region.
• Previous methods like polarizable embedding (PE) have limitations in describing environmental effects.

Purpose of the Study:

• To present the theory and implementation of the polarizable density embedding coupled cluster (PDE-CC) model.
• To combine the accuracy of coupled cluster (CC) theory with the efficiency of polarizable density embedding (PDE).
• To provide a robust method for studying chemically important core regions within complex environments.

Main Methods:

• Implementation of the PDE model within the Dalton quantum chemistry program's CC code.
• Description of the core region using high-level CC methods.
• Modeling the environment using fragment densities (from Hartree-Fock or KS-DFT) and anisotropic polarizabilities for the inner region.
• Utilizing distributed multipoles and polarizabilities for the outer region, similar to the PE model.
• Inclusion of electrostatic, polarization, and nonelectrostatic (Pauli/exchange) interactions via one-electron operators.

Main Results:

• Successful integration of PDE with CC theory (PDE-CC) in the Dalton code.
• The PDE-CC method efficiently accounts for environmental effects on the core region.
• The model accurately captures the response of the environment to changes in the core electron density, crucial for electronic transitions.

Conclusions:

• The PDE-CC method offers a computationally efficient and accurate approach for quantum chemistry.
• This model significantly enhances the study of electronic properties in condensed phases and complex molecular systems.
• PDE-CC provides a powerful tool for understanding chemical phenomena influenced by environmental interactions.