Molecular dynamics simulation of liquid trimethylphosphine

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Liquid trimethylphosphine (TMP) is a molecule with unique structural and dynamic properties.
• Understanding these properties is crucial for various chemical and material applications.

Purpose of the Study:

• To investigate the structural and dynamical properties of liquid TMP as a function of temperature.
• To analyze the behavior of TMP molecules using molecular dynamics simulations.

Main Methods:

• Molecular dynamics (MD) simulations were employed to study liquid TMP.
• A validated force field, derived from molecular mechanics and quantum chemistry, was used.
• Structural analysis included radial distribution functions (g(r)) and static structure factor (S(k)).
• Dynamical properties were assessed using time correlation functions.

Main Results:

• The force field accurately reproduced experimental TMP density at room temperature.
• At short distances, liquid TMP exhibits orientational correlations due to dipole-dipole interactions, despite behaving like a simple liquid based on center-of-mass distances.
• At high temperatures, diffusion, reorientation, and structural relaxation occur concurrently.
• Below approximately 220 K, a decoupling of dynamic properties is observed, with rattling dynamics becoming prominent due to the cage effect.

Conclusions:

• Liquid TMP displays complex behavior, combining characteristics of simple liquids with significant orientational correlations.
• Temperature plays a critical role in the dynamics of TMP, influencing diffusion, reorientation, and molecular motion.
• The onset of rattling dynamics below 220 K signifies a transition in the liquid's behavior.