Low-energy channel for mass transfer in Pt crystal initiated by molecule impact

RI Babicheva and I Evazzade and EA Korznikova and IA Shepelev and K Zhou and SV Dmitriev, COMPUTATIONAL MATERIALS SCIENCE, 163, 248-255 (2019).

DOI: 10.1016/j.commatsci.2019.03.022

Crystal surface bombardment by atoms or molecules, neutral or ionized, occurs both in ambient conditions and in many technological operations, such as surface plasma treatment, ion implantation, etc. Recently, it was established that the impact of a molecule initiates the mass transfer in the one-dimensional Frenkel-Kontorova atomic chain more efficiently than that of a single atom. This is explained by the fact that the atom can initiate only a very sharp, fast-moving crowdion (anti-kink), which requires relatively high energy, while the molecule is able to initiate a less localized crowdion with considerably lower velocity and energy. In the current study, by means of molecular dynamics simulation, for the first time, this phenomenon is studied for a realistic 3D model of platinum crystal. We compare the efficiency of single Pt atom impact and Pt-2 molecule impact on the (101) surface of fcc Pt crystal for the initiation of mass transfer in the material by crowdions. It is revealed that in order to generate a crowdion moving inside the crystal, the properly oriented molecule needs an order of magnitude smaller energy than single atom. This considerable reduction of required energy happens when the molecule is oriented perpendicularly to the crystal surface and hits the crystal along a close-packed atomic row. Furthermore, it is revealed for the first time that the molecule with sufficiently large velocity can initiate the socalled supersonic 2-crowdion, which travels longer distances in the crystal than the classical supersonic crowdion having same or even higher energy. Our results can be useful for understanding and prediction the mass transfer during technological applications where bombardment by atomic clusters is employed to modify and improve mechanical or functional properties of surfaces.

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