Interfacial properties of square-well chains from molecular dynamics simulation

ABSTRACT

Square-well (SW) potential is likely the simplest potential describing attractive and repulsive interactions. However, its discontinuous functional form makes it difficult to be used in Molecular Dynamics (MD) simulation, particularly with commercial MD packages. Recently, Zerón and collaborators [Mol. Phys. 116, 3355 (2018)] have presented a parameterisation of the SW potential that allows its use for simulation packages since the intermolecular potential and force are described by continuous mathematical functions. It was validated for SW spheres. In this work, we use this reported continuous SW potential to describe for the first time the equilibrium and interfacial properties of SW chains, with potential ranges of $\lambda =1.5$ and 1.75. Simulations for tetramers interacting with $\lambda =1.5$ are compared with available computational data in the literature, which has allowed to validate the method for molecular chain systems. Besides, a systematic study for the potential range of $\lambda =1.75$ has not been addressed so far, which represents valuable information for instance to discern whether different microscopic theories are capable of describing this type of system. In particular, we assess the effect of temperature, chain length, and potential range on the calculated properties, namely density profiles, coexistence densities, vapour pressures, surface tensions and critical points. Overall, with increasing the chain length, the width of the envelope of the coexistence phase increases, which results in an increase of the surface tension as well as the critical temperature at the same time that the vapour pressure and the interfacial width decrease.

GRAPHICAL ABSTRACT

KEYWORDS:

• Molecular dynamics
• interfacial properties
• square-well chains
• vapour-liquid phase equilibria

Acknowledgments

The authors thank the Centro de Supercomputación de Galicia (CESGA, Santiago de Compostela, Spain) for providing access to computing facilities.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financed by Spanish Ministerio de Ciencia e Innovación [grant number PID2021-125081NB-I00], Conserjería de Universidad, Investigación e Innovación (Junta de Andalucía) [grant number P20-00363], and Universidad de Huelva [P.O. FEDER - UHU - 1255522 and FEDER - UHU - 202034], all four co-financed by EU FEDER funds, and Universidad de Huelva.