Isomerization dynamics and thermodynamics of ionic argon clusters

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Understanding the behavior of atomic clusters is crucial for fields like materials science and physical chemistry.
• Argon clusters, particularly ionized ones, serve as model systems for studying fundamental chemical and physical processes.

Purpose of the Study:

• To investigate the dynamics and thermodynamics of small ionized argon clusters (Ar(n)+, n=3, 6, 9).
• To correlate thermal behavior with the charged core's nature and explore isomeric transformations.

Main Methods:

• Utilizing molecular dynamics (MD) and exchange Monte Carlo (MC) simulations.
• Employing a diatomic-in-molecule Hamiltonian for the electronic ground state potential energy surface.
• Applying a projective partition of kinetic energy for MD simulations and a charge localization order parameter.

Main Results:

• MD and MC simulations show agreement in microcanonical caloric curves when angular momentum conservation is enforced.
• Ar(3)+ is stable linearly up to 300 K, then isomerizes to a T-shaped structure.
• Ar(6)+ and Ar(9)+ feature a trimer core; solvent shell melting leads to core changes, and at high energies, the core becomes metastable, forming Ar(2)+ solvated by argon atoms.

Conclusions:

• The study provides insights into the structural evolution and phase transitions of ionized argon clusters under varying thermal conditions.
• The findings highlight the interplay between the charged core and neutral solvent atoms in determining cluster stability and dynamics.
• The methods employed offer a robust framework for studying similar atomic and molecular systems.