Comparison of microhydration methods: protonated glycine as a working example

Area of Science:

• Theoretical Chemistry
• Computational Chemistry
• Physical Chemistry

Background:

• Determining microsolvated complex structures and energies is challenging due to the combinatorial explosion of possible aggregates.
• Previous methods like chemical intuition and evolutionary trees exist but may not be exhaustive.

Purpose of the Study:

• To compare computational protocols for identifying stable geometries and interaction energies of microhydrated protonated glycine.
• To evaluate the effectiveness of hierarchical and Darwinian tree approaches for microsolvation studies.

Main Methods:

• A hierarchical approach combining AMOEBA search with DFT and MP2 refinements.
• A Darwinian tree approach using evolutionary logic and counterpoise-corrected MP2 calculations.
• Comparison of computed structures and interaction energies against experimental complexation enthalpies.

Main Results:

• Both hierarchical and Darwinian tree approaches yield similar conclusions regarding stable microsolvated structures.
• Certain unique structures were identified by only one of the two computational strategies.
• The study validates computational approaches against available experimental data for protonated glycine.

Conclusions:

• Employing multiple minima search tactics is essential for comprehensively identifying all possible microsolvated complexes.
• Combining different computational strategies enhances the reliability and completeness of structural predictions.
• This work provides insights into optimizing theoretical methods for studying solvation effects.