[Analysis Example]Nanotribology (Abrasive wear, Nanofabrication)

Molecular simulations are increasingly being applied to fields related to nanotribology, such as friction, wear, and fabrication at the nanometer scale [1]. Phenomena observed on the macroscale, such as roughness and stick-slip on the micrometer scale, need to be taken into account. On the other hand, the effects of atomic interactions are more significant at the nanoscale.

Fig.1 shows a demonstrative simulation of abrasive wear or nanofabrication at the nanometer scale, based on the references [2,3]. Molecular Dynamics (MD) calculations using LAMMPS are performed on the structure modeled using J-OCTA. Density Functional Theory (DFT) calculation using SIESTA was applied to estimate the potential between the sapphire (alumina single crystal) and iron, and EAM potentials were applied to the iron inside. We can see how the sapphire pressed against the iron surface penetrates and wears away at the iron surface (abrasive wear).

Of course, considering the spatial and time scales that can be handled by molecular dynamics, the discussion is limited (10nm : limited to the surface layer and often not knowing what the real structure is like. 10-100nsec : deformation is faster than actual measurement)[4], but by evaluating the horizontal/vertical forces, the friction coefficient at the nanoscale can be evaluated. It is expected to be applied to nanoscale fabrication of semiconductor materials such as silicon (e.g. CMP (Chemical Mechanical Polishing)).

If you are interested in such calculations, please feel free to contact us.

Fig.1. Grinding process of iron surface with sapphire at nanoscale
(left)  early time stage, (right) late time stage