Molecular dynamics of linear and branched alkanes

Abstract

We have extended a recently introduced united atom model of n-alkanes to investigate the liquid-state dynamics of squalane, a molecule with six, symmetrically placed, methyl side groups. We compare our results with experimental measurements of diffusion in the same system and with experimental and simulation results on n-decane and n-tetracosane. The model reproduces the significantly different temperature dependence of diffusion in squalane and n-alkanes of similar mass. The results of a detailed comparative study of the intrachain local dynamics in the different molecules makes apparent its correlation with global single-chain relaxation processes. For linear alkanes, we also make a comparison between united atom and asymmetric united atom models.

Atomistic Molecular Dynamics Simulations of Carbon Dioxide Diffusivity in n-Hexane, n-Decane, n-Hexadecane, Cyclohexane, and Squalane

“…One should notice that at the particular state point of 423.15 K and 1 MPa, which corresponds to the lowest density considered, all models examined showed the least accurate behavior. Earlier studies for pure n-alkanes by Mondello et al [62][63][64] have shown overestimation of self-diffusion coefficients by UA force fields.…”

Rheological and structural studies of liquid decane, hexadecane, and tetracosane under planar elongational flow using nonequilibrium molecular-dynamics simulations

“…The vertical lines in the figure represent the "critical elongation rate," ˙c, at which the product of a characteristic relaxation time and ˙͑note the Weissenberg number, 1 We= ˙͒ is equal to unity, and which is often approximately considered as the boundary between the linear and the nonlinear regimes in flowing systems. We calculated the critical elongation rate based on the results of = 58 ps for decane and = 531 ps for tetracosane by Mondello and Grest, 25 and = 188 ps for hexadecane by Cui et al 15 Using those values, the reduced critical elongation rates are found to be ˙c͑m 2 / ͒ 1/2 = 0.0406, 0.0125, and 0.004 43 for decane, hexadecane, and tetracosane.…”

Molecular dynamics simulations of the surface tension of n-hexane, n-decane and n-hexadecane

“…Figure 2. Comparison of the liquid coexistence densities, for n-hexane (top), n-decane (centre) and n-hexadecane (bottom) at coexistence, as a function of temperature, for the present work, the Gibbs ensemble results [2], the results from Alejandre et al molecular dynamic simulations [11] and experimental results concerning hexane [26].…”