| The heredity and selective heredity of configurations in some liquid metals or alloys during rapidly solidified processes have been found by molecular dynamics (MD) simulation, but the electronic machanism of the heredity and evolution of configurations has not been understood yet up to now. Supported by Foundation of Ministry of Science and Technology of China (104939), the stability and evolution of Aln clusters were investigated by frist-principle calculation with the aid of transition state searching method so as to make clear why some liquid metal clusters have structural heredity, whereas the others will be transformed. The work is divided into four parts: the stability of Aln clusters, configuration evolution, decomposition and synthesis of Aln±m clusters.1. The energetics and electronic structure of neutral Aln (n=223, 55) clusters were calculated by CASTEP program. Several parameters such as the binding energy Eb, the HOMO-LUMO energy gapΔEH-L and the second difference of energiesΔ2E(n) were utilized to characterize and analyze the structure stability of Aln cluster. The results show the structure stability of Aln clusters increases with total atom number n addition. For Al7, Al11, Al13, Al19, Al23 clusters with a nearly filled covalence electron shell and a high geometrical symmetry, a higher structure stability than that of their neighbor Aln (n≠7, 11, 13, 19) clusters can be seen.2. Based on the experiments of Aln+m+ clusters decomposed by means of a isolated Al atom or cation, the disassociation route and mechanism of Aln+m+ (n+m≤13) clusters in the Aln ++Alm (n=112, m=112) mode were investigated by using Linear Synchronous Transit (LST) and Quadratic Synchronous Transit (QST) method. The ionization potential, the endothermic reaction heatΔHR-P and the dissociation barrier energyΔER-T of Aln+m+ (n+m≤13) clusters were calculated. Comparison ofΔHR-P andΔER-T in the disassociation route reveals the least energy of a isolated Al atom or cation from the Aln+m+ clusters is related to a biggerΔHR-P and a moreΔER-T must be provided, while a big cluster decomposites into two small clusters. The energetics difference between routes should be responsible for the preference of Aln+ (n=213) clusters dissociated by means of Aln+→Al+ Aln-1+ or Aln+→Al++ Aln-1.3. The configuration evolution and transformation of Aln (n=37, 13, 19) clusters were examined by LST method in CASTEP program. It is demonstrated that the stable configurations of Al3, Al4, Al5, Al6, Al7, Al13, Al19 clusters are triangle, rhombus, trapezia, octahedron, decahedron, icosahedron and double icosahedron, respectively. For Al6 and Al19 clusters there are metastable structures of parallelogram and octahedron, respectively, whereas in the Al3, Al4, Al5, Al7 and Al13 clusters, no metastable configuration is validated. There exist a large energy gap and a low energy barrier between the octahedron and the parallelogram of Al6 clusters, so the transformation from its metastable to stable structures is rather easy. By contrast, a small energy gap and a high energy barrier between the stable and metastable structures of Al19 clusters mean its configuration evolution from the octahedron to the double icosahedron hardly, therefore the metastable octahedron configuration of Al19 clusters can be extensively detected in experiments and simulations.4. The formation routes of stable Aln (n=213) clusters assembled by two small clusters were investigated in the framework of LST/QST method in DMol3 program. The results show the addition of one sole atom to a cluster, i.e., the growth process, is generally automatic exothermic reaction, except for the growth of non-crystal configurations on the basis of crystal clusters. For the association of one cluster with another, i.e., the coalescence process, usually, there exists reaction energy barrierΔER-T. Comparison of the reaction heatsΔHR-P and activation energyΔER-T suggests that the coalescence processes are more favorable than the growth processes for Aln (n=213) clusters. In the coalescence processes, the clusters with typical crystal symmetrical elements, i.e., the crystal clusters Aln (n=26, 89), have higher formation ability than those with fivefold or tenfold symmetrical axes, i.e., the non-crystal clusters Aln (n=7, 1013). The formation with non-crystal Al7 cluster as a precursor, i.e., Alm+Al7→Alm+7, is the most preferable in energetics for non-crystal clusters among the coalescence routes considered.5. By slightly displacing the atom position of product to set up the reactant, a new transition state searching method of LST/QST is improved in the molecular orbital DMol3 program, with the aid of the minimum energy path (MEP) in the climbing image nudged elastic band (CI-NEB) method. The energetics and electronic structures of several Al12C configurations as well as their configuration evolution were investigated. A new low symmetrical isomer of Al12C clusters with high stability, i.e., Cs-Al12C, at the energy valley in the MEPs has been successfully predicted. 6.Using LST/QST method in a molecular orbital DMol3 program based on density functional theory, with the aid of the MEP in the CI-NEB method, the preference of synthesis modes and routes of three characteristic Al13 clusters in the mode of Al6+Al7→Al13 were calculated and analyzed. The results show the synthesis process may be divided into two steps: the distortion stage and the configuration evolution stage. In the first stage, the metastable clusters, e.g., C5v-Al6, are forced to transform into stable structure. In the configuration evolution stage, two different cases exist. For the synthesis of crystal clusters it is an automatic exothermic reaction if all reactants being of typical crystal symmetrical elements, while an energy barrier must be overcomed if one of reactants having fivefold or tenfold symmetrical axes. For the formation of non-crystal clusters with fivefold symmetrical axes, generally it is an automatic exothermic process or an exothermic synthesis reaction with low energy barrier when synthesis reactants include non-crystal clusters such as D5h-Al7 clusters.In conclusion, the Al7 decahedron and the Al13 icosahedron with fivefold or tenfold symmetrical axes play a key role for the competition of the formation and evolution of non-crystal configurations in a supercooling liquid against the nucleation and growth of crystals. D5h-Al7 and Ih-Al13 with magic number character have high stability and no isomer, so these clusters have heredity to some extent. Owing to liquid metals or alloys similar to amorphous structures being composed of small non-crystal configurations, the preference of the nucleation and growth of crystals during exothermic solidification process can be attributed to the high association and synthesis ability of crystal clusters on the basis of these small non-crystal configurations such as D5h-Al7 and Ih-Al13 clusters. A potential evolution among non-crystal clusters from a small D5h-Al7 cluster to medium Al10Al13 clusters even to larger Al19 and Al55 clusters as well as their defective structures should be responsible for the formation of the glassy state. Therefore the non-crystal or qusicrystal solids can't be obtained unless the icosahedron clusters in liquid are freezed and passed down to solid structures during non-equilibrium conditions.
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