Structural evolution of a Si melt in nanoscale confined space

Molecular dynamics (MD) simulations are performed to systematically study the structural evolution of a Si melt confined in nanoscale space. The freezing Si structure at 300 K is stratification which is composed of a stable crystalline shell and a metastable glassy core. Due to the spatial restriction effect, the confined structure consists of higher-coordinated clusters compared to the bulk Si. It is revealed that the statistical average of the ordered shell and the disordered core gives rise to the split of the second peak of the pair distribution function curves of the Si melt. Moreover, increasing the cavity size is detrimental to the stability of the layered configuration of the confined melt and increasing the cooling rate mainly influences the arrangement of Si atoms adjacent to the SWCNT wall. Interestingly, we also find that the cylindric cavity is more beneficial than the square one in inducing the formation of long-range crystalline order in nanoscale space.