ACKS2: atom-condensed Kohn-Sham DFT approximated to second order.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Materials science

Background:

• Polarizable force fields (PFFs) are crucial for simulating molecular systems.
• Existing methods like Electronegativity Equalization Method (EEM) have limitations in accuracy and scalability.
• Accurate computation of atomic charges and polarizability is essential for understanding material properties.

Purpose of the Study:

• To introduce a novel polarizable force field, ACKS2, for efficient and accurate calculations.
• To address limitations of previous methods in describing charge distribution and size-dependence.
• To provide a computationally efficient approach derived from Kohn-Sham density functional theory.

Main Methods:

• Development of atom-condensed Kohn-Sham density functional theory approximated to second order (ACKS2).
• Incorporation of constrained atomic populations and Legendre transform of Kohn-Sham kinetic energy.
• Extension of the Electronegativity Equalization Method (EEM) with novel theoretical underpinnings.

Main Results:

• ACKS2 accurately predicts atomic charges and linear response properties for extended systems.
• The new method demonstrates linear size-dependence of dipole polarizability in the macroscopic limit.
• Correct description of charge distribution during molecular dissociation is achieved.

Conclusions:

• ACKS2 offers an efficient and accurate alternative to existing polarizable force fields.
• The method overcomes key shortcomings of the Electronegativity Equalization Method.
• ACKS2 parameters are derived from fundamental atomic properties, enhancing transferability.