Figure 1

Anomalous liquid state of Al-Cu nanoalloys. (a) The color map of the simulated heat capacity $C(N_{\mathrm{Cu}},T)$ of ${\mathrm{Al}}_{55\mathrm{\text{−}}{N}_{\mathrm{Cu}}}{\mathrm{Cu}}_{N_{\mathrm{Cu}}}$ nanoalloys is shown for a different number of Cu atoms ($N_{\mathrm{Cu}}$) and temperatures ($T$). For some compositions that we did not consider here, we used interpolated values for the map. For each simulated $N_{\mathrm{Cu}}$, the peak positions of the simulated heat capacity are marked by dots. The solid lines connecting the dots represent phase boundaries between two liquid states $L$ and $L^{*}$ and one solid state $S$. In (b)–(c), two representative heat capacity curves are shown for $N_{\mathrm{Cu}}=10$ and 13, respectively. (d) The simulated isotherms of dynamic viscosity ($\mu$) of the Al-Cu nanoalloys are shown for three different temperatures below $T_{\mathrm{LLC}}$. (e) The simulated kinetic viscosities ($\nu$) of bulk Al-Cu alloys at $T=1000\mathrm{K}$ are shown for compositions around $x_{\mathrm{Cu}}=0.25$ (filled boxes). The experimental isotherms of the kinetic viscosity (taken from Ref. 5) are also shown for comparison (filled and open circles).Reuse & Permissions

Figure 2

Short-to-medium-range surface order. (a) A representative ${\mathrm{Al}}_{42}{\mathrm{Cu}}_{13}$ cluster at $T=850\mathrm{K}$ is shown. The atoms of the pentagonal SRO clusters (Al, yellow; Cu, red) are highlighted for contrast with the disordered atoms (gray). A schematic figure below illustrates a percolationlike cluster of the SRO structures (represented by dots) with a size $s_{\max }=7$, forming an MRO cluster. (b) Two representative probability distributions ($P_{\mathrm{SRO}}$) of $N_{\mathrm{SRO}}$ are given for the ${\mathrm{Al}}_{42}{\mathrm{Cu}}_{13}$ at $T=850$ (filled circle and black line) and 1300 K (open circle and blue line). (c) The plot of $\kappa =\Delta ⟨s_{\max }⟩/\Delta N_{\mathrm{SRO}}$ shows a percolationlike transition from the SRO liquid state to the MRO liquid state with a threshold $N_C=9$. For different compositions ($N_{\mathrm{Cu}}=10$ and 13) and temperatures, (d) the number of the pentagonal clusters $⟨N_{\mathrm{SRO}}⟩$ and (e) the order parameter $P_{\mathrm{MRO}}$ are presented. In (f), the viscosity $\mu$ is compared for $N_{\mathrm{Cu}}=10$ and 13 as a function of temperature above $T_m$. The difference of the two viscosity curves (filled square) is also given to show the additional component of $\mu$ for the $L^{*}$ state below $T_{\mathrm{LLC}}$.Reuse & Permissions

Figure 3

Percolated network of the fivefold SRO clusters in bulk liquid ${\mathrm{Al}}_{75}{\mathrm{Cu}}_{25}$. (a) A representative snapshot of the ${\mathrm{CuAl}}_3$ alloy in liquid state at $T=1000\mathrm{K}$ (Al, yellow; Cu, red). Here, only the 1551 pairs and the associated pentagonal rings are chosen from the bulk liquid to illustrate the clustering of the fivefold SRO structures. The inset shows an isolated SRO structure. (b) Probability distributions ($P_{\mathrm{SRO}}$) of the number of the 1551 pairs ($N_{\mathrm{SRO}}$) in a 256-atom supercell are given for the ${\mathrm{Al}}_{75}{\mathrm{Cu}}_{25}$ (filled circle and red line) and pure Al (open circle and black line) liquid states at $T=1000\mathrm{K}$. (c) Percolation probability ($P$) is shown as a function of $N_{\mathrm{SRO}}$. The vertical dashed lines in (b)–(c) denote the estimated percolation threshold.Reuse & Permissions