Calculation of diffusion coefficient of long chain molecules using molecular dynamics

• Molecular dynamics simulation coupled with Einstein relationship is employed to determine the diffusivity of two important long chain molecules MHA and ODT.
• Diffusivities are calculated at different temperatures in a humid environment containing few number of water molecules.
• Simulations are performed based on four different types of forcefield, one of which is general atomic parameter based (UFF) and the other one is ab initio data based (COMPASS). Another two forcefields are CVFF and PCFF which are also used for diffusivity calculation to show an overall comparison of the results.

Molecular dynamics (MD) is a powerful tool for calculating several thermo-physical properties of wide range of materials. In this study, the diffusivities (D) of two widely used long chain molecules MHA and ODT are calculated at various temperatures using MD simulations coupled with Einstein relationship. Four different kinds of forcefields COMPASS, UFF, CVFF and PCFF are employed in the MD simulation and the results are compared. Diffusivity values are evaluated in a humid environment in presence of water molecules.

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