DFT Functionals for Modeling of Polyethylene Chains Cross-Linked by Metal Atoms. DLPNO-CCSD(T) Benchmark Calculations

Area of Science:

• Computational Chemistry
• Materials Science
• Quantum Chemistry

Background:

• Polyethylene (PE) chains can be cross-linked by metal atoms, forming complexes with unique properties.
• Understanding the binding energies (BEs) of these cross-linked structures is crucial for predicting their behavior.
• Accurate computational methods are needed to model these complex interactions.

Purpose of the Study:

• To benchmark various Density Functional Theory (DFT) functionals for calculating binding energies of metal-atom-cross-linked polyethylene (PE) chains.
• To compare the performance of DFT functionals against high-level coupled-cluster methods (DLPNO-CCSD(T) and DLPNO-CCSD(T1)).
• To identify accurate DFT functionals for modeling both closed-shell and open-shell PE-metal complexes.

Main Methods:

• DFT functionals were combined with three dispersion corrections and two basis sets (def2-TZVPP, def2-QZVPP).
• Binding energies were calculated for model species PEX-M-PEX and PEX···PEX, where X represents 3-9 carbon atoms and M is a metal atom.
• Results were benchmarked against DLPNO-CCSD(T) for closed-shell complexes (M = Be, Mg, Zn) and DLPNO-CCSD(T1) for open-shell complexes (M = Li, Ag, Au).

Main Results:

• Five DFT functionals achieved accuracy within 5% for closed-shell PEX-M-PEX complexes.
• Fewer functionals were accurate for open-shell complexes, with only two deviating by less than 15% from DLPNO-CCSD(T1).
• PEX-Li-PEX complexes proved particularly challenging for the tested functionals.
• Range-separated hybrid functionals ωB97X-D3 and CAM-B3LYP/D3(BJ)-ABC demonstrated reasonable overall performance across all complexes.

Conclusions:

• DFT functionals show varying accuracy in predicting binding energies for metal-atom-cross-linked polyethylene chains.
• Specific functionals, particularly range-separated hybrids, offer a good balance of accuracy and efficiency for these systems.
• Further refinement of DFT methods may be needed for highly accurate predictions of open-shell metal-PE complexes.