(226aq) An Interatomic Potential for the Interfacial Characterization of Titanium and Polyethylene Based on the Modified Embedded-Atom Method

The modified embedded-atom method (MEAM), which is a reactive semi-empirical interatomic potential and was developed originally for the atomistic simulations of metals and metal alloys as well as metal hydrides, oxides, nitrides, and carbides, was recently parameterized for saturated hydrocarbons and related polymers, such as polyethylene and polypropylene, by the same research group [1]. This interatomic potential successfully predicts the energetics and geometries of linear and cyclic alkanes as well as alkyl radicals and reproduces the pressure-volume-temperature (PVT) relationships for these materials with great accuracy. The key advantages of the MEAM potential are 1) single formalism for metals, hydrocarbons, polymers, etc. that enables the simulations of complex material systems involving defects, free surfaces, and interfaces, 2) reactive simulation involving bond breaking and bond formation suitable to study damage and failure as well as chemical reactions in the atomistic and molecular scale, 3) computational efficiency due its simple formalism. The MEAM potential is widely used for the atomistic simulations of metals and metal alloys and its extension to hydrocarbons has enabled great many potential applications for polymer/metal material systems. In this work, we studied the interfacial energetics of polyethylene in contact with elemental titanium (Ti) surface. Ultra-high molecular weight polyethylene (UHMWPE) and Ti are two materials used in many biomedical applications, such as prosthetic joint materials (knee replacement). To enable the interfacial simulation of single- and multi-chain PE in contact with a Ti surface, we parameterized the MEAM potential for the Ti/C/H system of elements starting with our recently published set of carbon, hydrogen, and CH diatomic parameters [1]. For Ti, we used the parameters published by Kim and Lee [2] for the Ti-C binary system. We utilized the first-principles interaction energy data for the Ti-C, and Ti-H diatomics as the fitting database. Once parameterized, we used the MEAM potential to perform NVT dynamics simulations to calculate the energetics of PE/Ti interfacial interactions as well as to determine the conformations of single- and multi-chain PE on the Ti surface. The details of potential parameterization and molecular dynamics simulations as well as key findings will be presented.

[1] S. Nouranian, M. A. Tschopp, S. R. Gwaltney, M. I. Baskes, and M. F. Horstemeyer, "An Interatomic Potential for Saturated Hydrocarbons Based on the Modified Embedded-Atom Method," Physical Chemistry Chemical Physics, vol. 16, pp. 6233-6249, 2014.

[2] Y.-M. Kim and B.-J. Lee, "Modified embedded-atom method interatomic potentials for the Ti–C and Ti–N binary systems," Acta Materialia, vol. 56, pp. 3481-3489, 2008.