Ga-Al纳米合金的比块体熔化行为表征
Characterizing the greater-than-bulk melting behaviour of Ga-Al nanoalloys
摘要：
相图是预测系统中相变的最可靠的方法。在这项工作中，我们创建的相图的Ga（20-x）Al（x）+的团簇系统，其中的monohydrates团簇显示比块体熔化行为。在微正则系综中采用第一性原理Born-Oppenheimer分子动力学，我们描述了两种不同组分Ga 11 Al 9+和Ga 3 Al 17+的类固-液相变.团簇的比热峰值分别在824 K和922 K，高于相应的块体合金熔化温度。均方位移，扩散系数和原子分子分析强调内部和表面原子的环境之间的差异。内部和表面位点（或原子）可以随温度交换位置的“容易性”的Arbangius式描述用于量化比块体熔化特征更快的熔化特征，这证实了Ga（20-x）Al（x）+团簇是相应块体合金材料的残余物的观点，其具有特定于其尺寸和组成的附加特征。
英文摘要：
Phase diagrams are the most reliable way of predicting phase changes in a system. In this work, we create the phase diagram of the Ga(20-x)Al(x)+ bimetallic cluster system, for which the monometallic clusters display greater-than- bulk melting behaviour. Employing first-principles Born-Oppenheimer molecular dynamics in the microcanonical ensemble, we describe the solid-liquid-like phase transition in two distinct compositions Ga11Al9+ and Ga3Al17+. The clusters show peaks in specific heat at 824 K and 922 K respectively which is above the corresponding bulk alloy melting temperatures. Mean squared displacements, diffusion coefficients and atoms-in-molecules analysis emphasise the differences between the environments of the internal and surface atoms. An Arrhenius-like description of the 'ease' with which internal and surface sites (or atoms) can exchange positions with temperature is used to quantify the greater-than-bulk melting character which corroborates the view of a Ga(20-x)Al(x)+ cluster being a remnant of the corresponding bulk alloy material with additional characteristics specific to its size and composition.
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