Ab initio and DFT studies on methanol-water clusters.

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Molecular Interactions

Background:

• Understanding hydrogen bonding in molecular clusters is crucial for various chemical and physical processes.
• The interplay between methanol and water molecules in clusters influences their collective properties.
• Investigating cooperative effects provides deeper insights into intermolecular forces.

Purpose of the Study:

• To computationally investigate the structural, energetic, and spectral properties of methanol-water clusters.
• To analyze the hydrogen bonding network and the role of cooperativity in cluster stabilization.
• To compare the binding characteristics of pure water clusters with methanol-water mixed clusters.

Main Methods:

• Calculations employed Hartree-Fock, MP2, and DFT (B3LYP) methods for geometries, binding energies, and vibrational spectra.
• Bader's 'atoms in molecules' theory was used for hydrogen bond analysis.
• Natural bond orbital and reduced variational space decomposition analyses were performed to study cooperativity.

Main Results:

• Methanol and mixed clusters show higher binding energies than water clusters, attributed to the methyl group's electron-donating nature.
• Cooperative polarization and charge transfer effects enhance stability in methanol-containing clusters.
• Cooperativity contributes significantly to stabilization, increasing from 14% in trimers to 24% in tetramers.

Conclusions:

• The electron-donating methyl group in methanol strengthens binding in mixed clusters compared to pure water clusters.
• Cooperative effects play a vital role in the stabilization of methanol-water clusters, with increasing impact on larger clusters.
• Calculated vibrational frequencies show good agreement with experimental data, validating the computational approach.