Colloquium: Thursday, April 16, 4:10 PM, Lewis Lab 316
From Material Substance to Shape to Property
Boris I. Yakobson
Professor of Materials Science, Nano-Engineering, and Chemistry
Connecting the underlying chemical processes with the growth and emergent form remains unsurmountable problem in life sciences . In materials research, the current outlook is more optimistic: establishing such connection, from the basic interatomic forces to growing nanostructure shape and properties becomes a real possibility. We will discuss several important examples, focusing on two recent results. First one concerns the nanotubes, where it took two decades to derive a kinetic formula  R ~ sin x (growth rate R, helical angle x). Further analysis of the subtle balance between the kinetic and thermodynamic views reveals sharply peaked abundance distribution A ~ x exp (-x) . This explains the puzzling (n, n-1) types observed in many experiments. In the second example, a combination of DFT and Monte Carlo models explains the low symmetry shapes of graphene on substrates. In equilibrium, edge energy variation dE manifests in slightly distorted hexagons. In growth, it enters as ~exp(-dE/kT), amplifying the symmetry breaking to triangle, ribbon, rhomb .
 On Growth and Form, by D’Arcy W. Thompson (Cambridge U, 1917).
 F. Ding et al. PNAS 106, 2506 (2009); R. Rao et al. Nature Mater. 11, 213 (2012).
 V. Artyukhov - E. Penev et al. Nature Comm. 5, 489 (2014).
 Y. Liu et al. PRL 105, 235502 (2010); V. Artyukhov et al. PNAS 109, 15136 (2012); Y. Hao et al. Science, 342, 720 (2013); V.
Artyukhov et al. PRL, in press (2015).
Physics and Astronomy Colloquia are usually scheduled for Thursdays at 4:10 PM in Lewis Lab room 316. Refreshments and snacks are available in the nearby coffee room at 3:45 PM.
Physics Colloquium Schedule for SPRING 2015
Click on Title below for past or upcoming Announcements (where available), and Speaker name for website.