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Jens 'n' Frens
Idle thoughts of a relatively libertarian Republican in Cambridge, MA, and whomever he invites. Mostly political.
"A strong conviction that something must be done is the parent of many bad measures."
-- Daniel Webster
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Tuesday, November 11, 2003 :::
Nanoscopic clusters of gallium atoms, consisting of as few as 17 atoms, melt at much higher temperatures than bulk gallium, according to recent research at the Indiana University. The observation runs counter to theoretical expectations of melting points for small clusters. In fact, current theory suggests that the melting point should fall as a cluster size is reduced, and that nanoscopic lumps of many materials should be liquid at room temperature. In previous work, the researchers discovered similar trends in the melting of tin clusters, but did not observe melting transitions directly. Instead they monitored the shapes of small clusters to determine their state. In the recent experiment, the researchers launched the gallium clusters through a high pressure collision cell where they were heated in collisions with a helium buffer gas. By monitoring the portion of dissociated clusters that exited the collision cell, the researchers could directly determine the clusters' melting temperatures. While bulk gallium melts at 303 K, thirty-nine and forty atom gallium clusters melt at about 550 K, and seventeen atom clusters show no sign of melting at temperatures as high as 800 K. No theoretical framework currently exists to explain the high melting temperatures of gallium clusters. I can't honestly explain why I find this so interesting.
::: posted by dWj at 4:44 PM
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