Self-interaction correction in water-ion clusters

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Density functional approximations (DFAs) are crucial for studying molecular systems.
• Self-interaction error (SIE) is a known limitation in DFAs, affecting accuracy.
• Water-ion clusters are important model systems in chemistry and biology.

Purpose of the Study:

• To investigate the impact of self-interaction errors on the binding energies of various water-ion clusters.
• To evaluate the performance of the Fermi-Löwdin orbital self-interaction correction (FLOSIC) method in mitigating these errors.
• To compare different density functional approximations (LSDA, PBE, SCAN) when corrected for self-interaction.

Main Methods:

• Employed the Fermi-Löwdin orbital self-interaction correction (FLOSIC) method.
• Utilized local spin-density approximation (LSDA), Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA), and SCAN meta-GGA.
• Calculated binding energies for hydrogen-bonded (water-hydronium, water-hydroxide, water-halide) and non-hydrogen-bonded (water-alkali) clusters.

Main Results:

• Self-interaction errors lead to overbinding in hydrogen-bonded water-ion clusters.
• FLOSIC significantly reduces these errors, improving agreement with higher-level calculations.
• Non-hydrogen-bonded water-alkali clusters are less affected by self-interaction errors.
• Self-interaction corrected PBE (PBE-FLOSIC) showed the lowest mean unsigned error (≤50 meV/H2O) for hydrogen-bonded clusters.
• The magnitude of self-interaction errors is cluster-size dependent.

Conclusions:

• Self-interaction correction is vital for accurately describing binding energies in hydrogen-bonded water-ion clusters.
• FLOSIC is a promising approach, but further refinements are needed to capture size-dependent variations accurately.
• PBE-FLOSIC offers a good balance of accuracy and computational efficiency for these systems.