First order approximation of polyatomic ion and neutral diffusion in neutral gases under arbitrary fields

Area of Science:

• Physical Chemistry
• Computational Physics
• Chemical Physics

Background:

• Predicting diffusion coefficients is crucial for understanding gas transport phenomena.
• Existing methods often struggle with complex molecular interactions and driven conditions.

Purpose of the Study:

• To develop and validate a trajectory-based computational method for predicting diffusion coefficients in dilute gases.
• To incorporate realistic molecular structures and interactions into diffusion coefficient calculations.

Main Methods:

• Coupling classical trajectory simulations with two-temperature kinetic theory.
• Utilizing density functional theory for molecular geometries and charge distributions.
• Implementing the method in the Mass Diffusivity Software (MaDiS).

Main Results:

• Accurate prediction of diffusion coefficients for neutral molecules (∼5% deviation) and ions across thermal to driven regimes.
• Successful capture of temperature dependence, molecular size effects, and anisotropic transport under electric fields.
• Validation against experimental data for diverse neutral and ionic systems.

Conclusions:

• The trajectory-based method provides a consistent and accurate approach for diffusion coefficient prediction.
• The inclusion of realistic molecular structure enhances the applicability to polyatomic ions.
• The MaDiS software offers a valuable tool for simulating gas transport properties.