Reactive Molecular Dynamics Study of Mechano-chemical Decomposition of Perfluoropolyether Lubricants in Heat-assisted Magnetic Recording

Abstract

To achieve effective lubrication of head-disk interface in heat-assisted magnetic recording (HAMR), mechano-chemical decomposition of nonpolar and polar perfluoropolyether (PFPE) lubricant films, i.e., Z, Z-tetraol, Demnum, and D-4OH, was investigated using reactive molecular dynamics. By fitting with quantum calculation results, the reactive force field (ReaxFF) for PFPE was developed, allowing simulation of chemical reactions of PFPE lubricants. The results showed that at a temperature of 700 K, pure thermal decomposition of PFPE hardly occurs within the nanosecond heating time of HAMR, whereas mechano-chemical decomposition is highly possible to occur when normal pressure and shear are applied by the head and disk. We confirmed that thermal decomposition is mainly caused by the dissociation of C–O bond at the polar end groups and mechano-chemical decomposition is caused by dissociation of C–O bonds at both the polar end groups and main chains.