A systematic investigation with density functional theory (DFT) was carried out in order to explore the structural, energetic and electronic properties of silicon-doped germanium (SiGen, n 1-20) clusters using SIESTA package. In this regard, isomers of SiGen clusters with the lowest-energy were determined and discussed. We found that the doping of Gen + 1 clusters with one Si atom enhances the stability of these clusters. The relative stability has been studied relative to cluster size in terms of binding energies, fragmentation energies and second-order difference of energies for all SiGen structures. Likewise, electronic properties such as HOMO-LUMO gaps, vertical electron affinity (VEA) and vertical ionization potential (VIP) were identified and analyzed as well. Maximum peaks of the fragmentation energy were observed at sizes n 3, 5, 8-11, 13, 15, and 17 for Gen + 1 and SiGen clusters, respectively, which indicates that these clusters have higher relative stability than their neighbors. Besides, the second energy difference analysis shows that Gen + 1 and SiGen clusters at n 2-8, 10-15, 19, 20 are more stable. The values of HOMO-LUMO gaps take a decreasing trend with the increasing number of Si atoms in the cluster, which suggest an increase in chemical activity. Also, through our discussion of parameters VEA and VIP we found that SiGe4 cluster has high metallic property. The obtained results revealed that the SiGe15 cluster with C2 symmetry is more stable than the other clusters.
In recent decades, powder metallurgy technology has advanced considerably and been used to manufacture sintered structural components with extremely high dimensional accuracy and excellent surface finish. This process is based on the compression of a mixture of metal powder and sintering in an oven using controlled temperature and atmosphere. This technology meets copper alloys design with excellent mechanical properties at the lowest cost. This prompted us to study the effect of sintering temperature and aluminum concentration on the hardness, microstructure, and density of copper-aluminum (Cu-Al) alloys prepared by using the powder compaction process. In this work, samples of Cu-Al alloy with 5, 11, 14, and 18 wt. % of Al were prepared by mechanical alloying of elemental powders, followed by consolidation under a pressure of 12.5 MPa and sintering at 700-1000 C in vacuum for 90 min. Microstructural constituents were examined using X-ray diffraction. Density and hardness were measured and their changes with the size of the granules and the formed phases were studied. The 2 phase samples showed higher hardness.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.