Molecular dynamics (MD) simulation was applied to the sintering behavior of silver nanoparticles on a gold substrate in order to elucidate the sintering mechanism of the nanoparticles on the substrate. The simulation revealed that silver atoms from 1 and 2 nm nanoparticles migrated freely because of their larger surface energy and then epitaxially reoriented to the gold substrate so as to reduce grain boundary energy. The silver nanoparticles were more spread out on the (011) gold substrate than on the (001) substrate, indicating that substrates with larger surface energy induce greater spreading rates. Consideration of the competition of neck growth and epitaxial growth in sintering of nanoparticles revealed that reduction of surface energy is the predominant driving force in the initiation of sintering of silver nanoparticles, and that the reduction of grain boundary energy is subsequently consequential.

Abstract. The melting points of 3d transition metal elements show an unusual local minimal peak at manganese across Period 4 in the periodic table. The chemical bonding properties of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper are investigated by the DV-X cluster method. The melting points are found to correlate with the bond overlap populations. The chemical bonding nature therefore appears to be the primary factor governing the melting points. IntroductionIn general, the melting points of transition metals are much higher than those of main-group metals. The outermost as well as inner shell electrons contribute to the bonding in transition metals. Across Period 4 in the periodic table, the melting points of 3d transition metal elements show a maximal peak around vanadium and chromium. Further, the melting points decrease from chromium to copper and zinc. However, the melting points show a local minimal peak at manganese. This behavior is not entirely clear although there have been attempts to explain the anomaly [1,2].In the present work, the chemical bonding properties of scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper are investigated by the DV-X cluster method to clarify the local minimal peak at manganese.

Abstract:The interfacial bonding utilizing Ag 2 O-derived silver nanoparticles was evaluated using TEM observation and molecular dynamics simulation. The TEM observation reveals that the crystal orientation of the sintered silver corresponded to that of the gold substrate. This is considered that the epitaxial layer of silver was formed through in-situ formation of silver nanoparticles from Ag 2 O paste, and oriented in the direction of the gold crystal. MD simulation successfully recreated the sintering behavior of silver nanoparticles and the gold substrate. The simulation results clearly showed the epitaxial layers of silver atoms were formed on the substrate. The existence of the closed pore indicates the acceleration of the sintering between nanoparticles and the gold substrate to minimize the total sum of surface energy and grain boundary energy.

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