Combining wavefunction frozen-density embedding with one-dimensional periodicity.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Condensed Matter Physics

Background:

• Accurate calculation of local properties in large molecular systems is computationally demanding.
• Existing methods often struggle with the balance between accuracy and computational cost for condensed phases.

Purpose of the Study:

• To introduce a novel computational method combining one-dimensional periodicity with frozen-density embedding (FDE).
• To enable efficient calculation of local properties in condensed molecular systems.
• To assess the accuracy and convergence of the new method for various molecular properties.

Main Methods:

• Implementation of periodic orbital-uncoupled FDE within the KOALA program.
• Explicit computation of electron density for the active subsystem only.
• Self-consistent relaxation of the active subsystem density in the environment potential.
• Application to calculate ground-state dipole moments, excitation energies, and ionization potentials.

Main Results:

• The developed method provides a fully self-consistent solution for condensed molecular systems.
• Local properties can be calculated efficiently by treating only a small active subsystem (2-3 molecules).
• Results are converged with respect to environmental contributions for small active subsystems.
• The method is applicable to various quantum chemical methods like configuration interaction and time-dependent density-functional theory.

Conclusions:

• The combination of 1D periodicity and FDE offers an efficient approach for studying local properties in condensed molecular systems.
• The method achieves converged results with minimal active subsystems, reducing computational cost.
• This implementation is suitable for calculating properties like dipole moments, excitation energies, and ionization potentials but not for metallic bonding due to the lack of band structure calculation.