Figure 1

Sn crystals encapsulated by graphitic onion-like shells. (a) Sn crystal (diameter 14 nm) superheated at 770 K. The lattice fringes of the core demonstrate the presence of Sn in the solid crystalline phase. The measured spacing of the fringes is 0.29 nm which corresponds to the (200) lattice planes of $\beta \mathrm{\text{−}}\mathrm{S}\mathrm{n}$. (b) Supercooled liquid Sn droplet (top, labeled with “liq”) at 370 K. The specimen was subjected previously to high temperature so that melting occurred. A bare (not encapsulated) Sn particle (bottom, labeled “sol”) has already solidified. Several adjacent particles overlap in the projection.Reuse & Permissions

Figure 2

Pb encapsulated by graphitic shells. (a) Crystalline Pb superheated at 740 K. The spacing of the lattice fringes is 0.29 nm, corresponding to the nominal spacing of the (111) planes (0.286 nm) in fcc crystals of Pb. (b) Liquid encapsulated Pb droplet (diameter ca. 30 nm) at 870 K.Reuse & Permissions

Figure 3

Volume per atom as a function of temperature at different applied external pressures for Pb, as obtained from isoshape isothermal-isobaric simulations. The volume change at the melting transition is approximately $0.85{\mathrm{\AA }}^3$ per atom in all three cases. The inset shows the mean-squared displacements (MSD) of the Pb atoms at a pressure of 2.5 GPa, and temperatures of 860 K (dotted line) and 870 K (solid line), i.e., just before and after the melting transition at this pressure. The flat MSD observed at 860 K results from thermal oscillations of the atoms around their equilibrium positions, indicating that the system is solid, while the finite slope of the solid curve at 870 K is typical of the diffusive behavior of the liquid state. From the slope of this curve a diffusion coefficient of $2.0\times {10}^{-5}\mathrm{c}{\mathrm{m}}^{\mathrm{2}}/\mathrm{s}$ can be deduced.Reuse & Permissions