Abstract

Structure and stability of nanometer-sized Ag₈₈₇, Au₈₈₇ and Ti₇₈₇ clusters soft-landed on graphite (at deposition energies E_dep = 0.001 − 5.0 eV per atom) are studied by means of molecular dynamics simulations. Parameters for the cluster–surface interactions are derived from complementary ab initio calculations. The shape and the contact angle of deposited clusters are systematically analyzed for different deposition energies and temperature regimes. The Ag₈₈₇ cluster deposited at E_dep ≲ 0.1 eV/atom undergoes collision-induced plastic deformation, thus acquiring an ellipsoidal shape with the contact angle close to 180°. In contrast, Au₈₈₇ and Ti₇₈₇ clusters undergo a collision-induced melting phase transition followed by their recrystallization; these processes lead to the formation of the droplet-like shapes of the clusters in a form of truncated spheroids. At larger deposition energies all clusters flatten over the surface and eventually disintegrate at E_dep ≈ 0.75 − 1.0 eV/atom (for Ag₈₈₇ and Au₈₈₇) and ≈3 eV/atom (for Ti₇₈₇). It is found also that the shape of deposited clusters is strongly influenced by the strength of cluster–substrate interaction and the corresponding interaction mechanism, namely the weak van der Waals interaction between metal and carbon atoms or the van der Waals interaction with an onset of covalent bonding. Similar phenomena should arise in the deposition of clusters made of other elements, which interact with a substrate by one of the above-described mechanisms.

Graphical abstract

中文翻译：

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金属簇在石墨上的软着陆：分子动力学研究

摘要

 通过分子动力学模拟研究了纳米软的石墨化Ag ₈₈₇，Au ₈₈₇和Ti ₇₈₇团簇的结构和稳定性（沉积能量E _dep = 0.001-5.0 eV /原子）。团簇-表面相互作用的参数是从互补的从头算起的。针对不同的沉积能和温度范围，系统地分析了沉积团簇的形状和接触角。银₈₈₇簇保藏在Ë _DEP  ≲为0.1eV /原子经历碰撞诱导的塑性变形，从而获取与接触角接近椭圆体形状，以180°。相比之下，Au ₈₈₇Ti ₇₈₇团簇发生碰撞诱导的熔化相变，然后发生重结晶。这些过程导致以截球形的形式形成簇状的液滴状形状。在更大的沉积能量的所有集群弄平整个表面，并最终崩解在Ë _DEP  ≈0.75 - 1.0电子伏特/原子（银₈₈₇和Au ₈₈₇）和≈3电子伏特/原子（钛₇₈₇）。还发现沉积的团簇的形状受团簇-底物相互作用的强度和相应的相互作用机理的强烈影响，即金属和碳原子之间的弱范德华相互作用或共价发生时的范德华相互作用粘接。在由其他元素制成的簇的沉积中应该出现类似的现象，这些簇通过上述机制之一与基板相互作用。

图形概要