Molecular Binding in Post-Kohn-Sham Orbital-Free DFT.

Area of Science:

• Quantum Chemistry
• Computational Materials Science
• Theoretical Physics

Background:

• Orbital-free density functional theory (DFT) offers a computationally efficient alternative to traditional Kohn-Sham DFT.
• Developing accurate noninteracting kinetic energy functionals is a key challenge in orbital-free DFT.
• Understanding molecular binding is fundamental to chemistry and materials science.

Purpose of the Study:

• To investigate molecular binding using post-Kohn-Sham orbital-free DFT.
• To explore the role of noninteracting kinetic energy functionals and effective homogeneity in molecular binding.
• To develop and test new functionals that satisfy density scaling conditions.

Main Methods:

• Utilized noninteracting kinetic energy functionals satisfying uniform electron gas conditions and density scaling.
• Introduced a parameter to quantify molecular binding.
• Fitted functionals to near-exact effective homogeneities and Kohn-Sham energies.
• Tested functionals on a series of 11 molecules.

Main Results:

• Molecular binding generally improves with better effective homogeneity, but requires accurate noninteracting kinetic energy.
• Optimal binding is achieved when both effective homogeneity and noninteracting kinetic energy are simultaneously accurate.
• A Thomas-Fermi-von Weizsäcker functional with a second gradient correction showed average molecular binding.
• The system-dependence of effective homogeneity was quantified.

Conclusions:

• Density scaling homogeneity considerations are vital for designing accurate noninteracting kinetic energy functionals.
• Simultaneous accuracy in effective homogeneity and noninteracting kinetic energy is key for reliable molecular binding predictions.
• The developed functionals offer a promising step towards more accurate orbital-free DFT calculations.