An innovative method for calculating partial molar volume from a standard molecular trajectory

Abstract

In this research, we present a novel method for calculating the partial molar volume (PMV) of system components through post-processing the output trajectory of a molecular dynamic simulation. The method involves employing linear regression and sampling small volumes from the system during the simulation time, to obtaining the PMV of its components. To validate our approach, simulations were conducted on two systems previously studied in the Journal of Molecular Liquids (386, 2023, 122498). A comparison between our results and experimental values revealed average relative deviations as minimal as 2.49 %, and specific sampling methods achieved even lower relative deviations, down to 1.21 % and 1.18 %. The average relative deviation across all components for the two systems was calculated at 7.24 %, translating to average deviations of 6.19 cm^3/mol for mesitylene and 7.80 cm^3/mol for isopropanol. To demonstrate the method's implications, we conducted simulations on a series of systems comprising model asphaltene, an organic solvent, and a chemical inhibitor. By analyzing the PMV results for the precipitant phase (asphaltene and inhibitor), we offer insights into the inhibition mechanism, showcasing how it enhances the solubility of the precipitants in the employed solvents. Finally, we aim to hypothesize a molecular-level explanation of the inhibition process through quantitative measures by comparing the size and number of nanoaggregates and exploring the molecular positioning within these aggregates. Our method introduces a valuable approach to calculate PMVs to comprehend the behavior of self-associating solutes and their interactions with solvents.