Equilibrium Bond Lengths from Orbital-Free Density Functional Theory.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Materials science

Background:

• The atomic fragment approach is an ab-initio, parameter-free method for modeling chemical bonding.
• It utilizes orbital-free density functional theory based on the bifunctional formalism, employing density and Pauli potential as variables.
• This approach can provide exact Kohn-Sham Pauli kinetic energy when using orbital-based data, allowing for orbital-free approximations.

Purpose of the Study:

• To investigate the effectiveness of artificial closed-shell fragments with non-integer electron occupation in modeling chemical bonding.
• To assess the performance of the atomic fragment approach in predicting bond lengths of diatomic molecules.
• To determine if modified fragments can better mimic molecular electronic structure than ground-state fragments.

Main Methods:

• Implementing the atomic fragment approach with artificial closed-shell fragments.
• Utilizing non-integer electron occupation for these fragments.
• Comparing the predicted bond lengths of diatomics with those obtained using ground-state fragments.

Main Results:

• The use of artificial closed-shell fragments with non-integer electron occupation improved bond length predictions for several tested diatomics.
• These modified fragments demonstrated an enhanced ability to mimic the electronic structure of molecules compared to ground-state fragments.
• The improvements in bond length prediction were consistent with electronic structure predictions.

Conclusions:

• Artificial closed-shell fragments with non-integer electron occupation represent a promising refinement for the atomic fragment approach.
• This modification can lead to more accurate modeling of chemical bonding and bond lengths in diatomic systems.
• The study highlights the potential of tailoring fragment electronic structure for improved computational chemistry predictions.