Convergence behaviour of solvation shells in simulated liquids

Area of Science:

• Computational chemistry
• Molecular dynamics simulations
• Physical chemistry

Background:

• Solvation shells discretize solvent positions around a solute.
• Two main definitions exist: solute-centric and locally defined.
• Local definitions may not be directly comparable.

Purpose of the Study:

• To analyze and compare properties of locally defined solvation shells.
• To investigate deviations from bulk properties in pure solvents.
• To propose a method for restoring convergence in shell analysis.

Main Methods:

• Simulations of five pure liquids of differing polarity.
• Local shell definition using radial distribution function minima and Relative Angular Distance (RAD).
• Analysis of potential energy, coordination number, and coordination radius.

Main Results:

• Locally defined shell properties deviate from bulk values, not converging.
• Deviations increase with shell index due to interconnectedness of molecules.
• RAD and water show amplified deviations due to structure and interactions.

Conclusions:

• Locally defined solvation shells are not directly comparable to solute-centric shells.
• Box size and cutoff influence shell convergence.
• A hybrid method is proposed to define shells for improved convergence.