Rotational dynamics of simple asymmetric molecules

Area of Science:

• Computational Physics
• Materials Science
• Chemical Dynamics

Background:

• Molecular systems exhibit complex relaxation dynamics, including alpha (structural) and beta (secondary) processes.
• Experimental studies on molecular dynamics often yield divergent results, necessitating a deeper theoretical understanding.
• The interplay between thermodynamic conditions, molecular properties, and analytical techniques influences observed relaxation behaviors.

Purpose of the Study:

• To investigate the influence of molecular symmetry and correlation function choice on alpha and beta dynamics in rigid diatomic molecules.
• To reconcile discrepancies observed in experimental measurements of molecular relaxation dynamics.
• To elucidate the underlying mechanisms governing the manifestation of secondary relaxation as an excess wing.

Main Methods:

• Rigid diatomic molecules were simulated using molecular dynamics.
• Simulations explored various thermodynamic conditions and analyzed dynamics using both odd and even correlation functions.
• Focus was placed on characterizing the emergence and merging of alpha and beta relaxation processes.

Main Results:

• Distinct alpha and beta relaxation dynamics were observed, with scenarios ranging from onset to merging behavior.
• Molecular symmetry and the type of correlation function (odd vs. even) significantly impacted relaxation profiles.
• The beta process contributed less to even-order correlation functions, explaining its varied intensity in different experimental techniques.

Conclusions:

• The study reconciles divergent experimental findings by demonstrating how simulation parameters affect observed dynamics.
• The choice of correlation function is critical for accurately interpreting secondary relaxation contributions.
• Understanding these simulation-dependent effects is key to accurate characterization of molecular dynamics.