MOLECULAR DYNAMIC MODELING OF INTERFACIAL ENERGY

Molecular dynamic modeling is used to calculate the changes in the ene rgy between two surfaces when the surfaces are first allowed to approa ch one another and, subsequently, separated. The equations of motion o f the atoms, which were assumed to interact via a Lennard-Jones potent ial, were integrated using Verlet's algorithm. They were implemented i n an environment of periodic boundary conditions, feedback loop temper ature and pressure controllers, with direct computation of the stress and strain tensors. This approach allows one to calculate the temperat ure dependence of the 'leap-to-contact' phenomenon, the thermodynamic work of adhesion, the work needed to separate the surfaces, and the fo rces of attraction and separation. Effects that occur during approach and separation, such as surface roughening and vacancy formation, were included in the energetics calculations. Sound waves and the resultin g thermal transients were also modeled. The adhesion hysteresis and ir reversible behaviors during approach and separation that arise from th ese calculations are discussed in detail.