Atomic ordering in the liquid adjacent to an atomically rough solid surface

Abstract

In this work, atomic ordering in the liquid adjacent to both crystalline and amorphous substrates with atomic level surface roughness was investigated systematically using molecular dynamics (MD) simulations. We found for the first time that increasing surface roughness of a crystalline substrate reduces both atomic layering and in-plane atomic ordering in the metallic liquid adjacent to the liquid/substrate interface. In addition, our MD simulation results revealed that the rough surface of an amorphous substrate eliminates completely in-plane ordering in the liquid regardless of surface roughness and reduces/eliminates atomic layering in the liquid depending on the level of surface roughness. This reduced atomic ordering in the liquid adjacent to an atomically rough surface can be attributed to the increase in mobility of atoms in the liquid compared with the case with a smooth crystalline surface. From the point of view of heterogeneous nucleation, in addition to the effect of lattice misfit investigated in our previous studies, this work provides further confirmation of the importance of structural templating as a mechanism for both prenucleation and heterogeneous nucleation. Furthermore, this work offers a new approach to impede heterogeneous nucleation by roughening the substrate surface at the atomic level.

Prenucleation at the Interface Between MgO and Liquid Magnesium: An Ab Initio Molecular Dynamics Study

“…[12,16] However, as shown in the literature, lattice misfit has little influence on the layering of the liquid atoms adjacent to the substrate. [23,24] Therefore, we can conclude that the weakened layering in the L-Mg/MgO{1 1 1} system originates from the atomically rough substrate surface, [26] since the atomically rough surface hinders the templating of substrate for liquid Mg to nucleate, according to the epitaxial nucleation/growth model. [11] Figure 4 also provides information about the interlayer spacing between the substrate surface layer and the 1st liquid Mg layer.…”

“…Prenucleation can be further quantified by atomic layering normal to the substrate/ liquid interface and in-plane atomic ordering parallel to the substrate/liquid interface. The recent studies of prenucleation have identified the following three factors that affect nucleation potency of a substrate [23][24][25][26] :…”

“…In general, a chemically affinitive substrate promotes prenucleation, whereas a chemical repulsive substrate has lower potency for heterogeneous nucleation. [25] Surface roughness: The recent classic molecular dynamics simulation [26] showed that atomically rough surface impedes strongly prenucleation by reducing both atomic layering and in-plane atomic ordering in the liquid adjacent to the substrate. Fig.…”

“…[11] Recently we investigated the chemical effect of potent substrates on prenucleation and found that a chemically affinitive substrate promotes prenucleation in the liquid at the liquid/substrate interface, whereas a chemically repulsive substrate impedes it. [25] In addition, Jiang et al [26] modeled the effect of substrate surface roughness on prenucleation using a classic atomistic MD technique. Their modeling revealed that atomic level surface roughness impedes significantly prenucleation.…”

“…Their modeling revealed that atomic level surface roughness impedes significantly prenucleation. [26] In light of such findings, it would be interesting to investigate the effect of interaction between MgO and liquid Mg on the prenucleation at the L-Mg/MgO interface.…”