Dynamic Heterogeneity in the Monoclinic Phase of CCl4.

Area of Science:

• Solid-state physics
• Materials science
• Computational chemistry

Background:

• Carbon tetrachloride (CCl4) possesses a stable monoclinic phase with significant rotational dynamics below 226 K.
• Nuclear quadrupolar resonance studies indicate CCl4 dynamics resemble other CBrnCl4-n compounds, suggesting glass-like relaxation in non-glass formers.
• Understanding molecular dynamics in crystalline solids is crucial for predicting material properties.

Purpose of the Study:

• To investigate the rotational dynamics of CCl4 in its monoclinic phase using molecular dynamics simulations.
• To elucidate the mechanisms behind the observed heterogeneous dynamics.
• To compare simulation findings with experimental nuclear quadrupolar resonance data.

Main Methods:

• Molecular dynamics simulations were employed to model the rotational motion of CCl4 molecules.
• Analysis of simulated trajectories focused on identifying and quantifying molecular rotations.
• A master equation approach was utilized to describe the rotational dynamics based on simulated rates.

Main Results:

• CCl4 molecules were observed to undergo C3-type, jump-like rotations around their C-Cl bonds.
• Simulated rotational dynamics were accurately reproduced using a master equation with experimentally derived rates.
• Heterogeneous dynamics were identified, stemming from variations in rotational rates associated with different axes and molecules within the unit cell.

Conclusions:

• The study confirms the presence of complex, heterogeneous rotational dynamics in crystalline CCl4.
• These dynamics, characterized by distinct rotational modes, are analogous to relaxation processes observed in glasses.
• Molecular dynamics simulations provide a powerful tool for understanding solid-state dynamics and validating experimental findings.