Hardness of Al-based quasicrystals evaluated via cluster-plus-glue-atom model

Catalytic activation of a non-noble intermetallic surface through nanostructuration under hydrogenation conditions revealed by atomistic thermodynamics

“…The bulk structures of Al 13 TM 4 compounds, considered as approximants to decagonal quasicrystals, are traditionally described as periodic piles of atomic planes perpendicularly to the pseudo 10-fold direction ([100] and [010] for Al 13 Co 4 and Al 13 Fe 4 , respectively), with pseudo-quasiperiodic in-plane atomic order. Like most intermetallic compounds 18 , they are also represented as a stacking of clusters, defined by geometric or electronic arguments [37][38][39][40] . This dual description leads to two typical models for the Al 13 Co 4 (100) and Al 13 Fe 4 (010) pseudo 10-fold surfaces, presented in Fig.…”

Study of elastic anisotropy for 1, 3, 5-trinitro-1, 3, 5-triazacyclohexane by supramolecular structural unit

“…构，保证了结构的对称性，但未考虑到结构稳定性 [20] 。因此，董等人提出"团簇 加连接原子"模型作为最小化学单元来有效地表征材料的结构信息。 "团簇加连接 原子"模型是指将材料的成分由团簇部分加上位于团簇间隙的连接原子部分描述。 其中，团簇可以理解为以任一原子为心的近邻配位多面体 [20][21][22][23][24] 。在团簇加连接原 子模型的结构基础上，可以有效地建立材料成分与力学性质的关联。陈等人构建 Al基准晶的团簇加连接原子模型并研究其维氏硬度，结果表明团簇式内约一半最 弱键断裂， 硬度值等于单位团簇体积内断裂最弱键的能量 [25] 。 基于以上理论背景， 本文提出超分子结构单元来研究RDX单晶的弹性各向异性，超分子结构单元指任 一分子与周围分子组成的近邻配位多面体。 董等人提出总原子数密度分布n(r)和Friedel振荡势(r)来确定金属玻璃的主团 簇。总分子数密度分布n(r)是指单位体积内包含的原子个数随距离的径向分布，记 为n(r)=N(r)/(4πr 3 /3)，其中N(r)表示半径为r的球内包含的总原子个数 [21] 。杂质电荷 引入电子体系时，杂质电荷的电子云密度由于极化作用重新分布，对于距离r处的 电子来说，其势能函数(r)正比于余弦函数，这种长程振荡即为Frield振荡，定义 Frield波长 Fr =2π/2k F ，k F 为费米波矢 [26] 。为了将n(r)与Friedel振荡势(r)进行对比， 根据 Fr =r 1 /1.25将半径r归一化，其中r 1 指Friedel振荡势(r)第一个波谷对应的半径， n(r)-r/ Fr 曲线表明n(r)曲线的波峰对应着(r)的波谷，反之亦然。金属玻璃的主团 簇位于(r)的第一个波谷处，此时原子分布满足球周期性，体系能量最低，结构最 稳定 [21,24,27]…”

Hidden electronic rule in the “cluster-plus-glue-atom” model

“…While the key point is determination of the principal cluster entering into the cluster formula: [cluster](glue atoms) x . To resolve this problem, an effective method of central force field model 29 60 has been developed by combining interatomic force constants ( IFCs ) 61 62 and atomic close packing principle 14 22 , while its general utility has been validated by different CMAs in numerous alloy systems 27 28 29 . For a given alloy phase, the central force field model shows that those atoms with the largest IFCs act as the central atom of the cluster, those atoms with the smallest IFCs act as the glue atoms of the model, while those atoms with the IFCs locating between the max.…”

“…Among these cluster-based models, Dong’s “cluster-plus-glue-atom” model 15 can be used to describe the atomic structure of nearly all materials. Denoted by a uniform cluster formula of [cluster](glue atoms) x 18 19 20 21 , this cluster-plus-glue-atom model regards the atomic structure of any materials, no matter whether crystalline or non-crystalline, to be composed of the clusters part and the glue atoms part 22 23 24 25 26 27 28 . Accordingly, all atoms in a given structure belong to three kinds of the central atoms, the shell atoms and the glue atoms 29 30 , as the red spheres, the blue spheres and the green spheres shown in Supplementary Figure S1 , respectively.…”