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SUMMARY:Simple microscopic models of complex systems - Professor Jeremy Sc
 hofield (University of Toronto)
DTSTART:20160520T110000Z
DTEND:20160520T114000Z
UID:TALK65736@talks.cam.ac.uk
CONTACT:Alex Thom
DESCRIPTION:The use of hard-core and square-well interaction potentials in
  the modelling of condensed phase systems has a long history dating back t
 o the study of virial expansions of the equation of state of a liquid in 1
 885.  Models based on these simple interactions continue to be useful sinc
 e such interaction potentials frequently capture the relevant physical cha
 racteristics of a system yet are analytically tractable.  In this talk som
 e illustrations of the use of discontinuous potentials are presented.\n\nF
 irst\, the construction of discontinuous potential models of protein-like 
 chains is discussed. It is shown that for a protein-like chain in which th
 e constituents interact via hard-core and square-well interactions\, the s
 tructure and folding dynamics of the system can be analyzed via a Markov s
 tate model in which the temperature dependence of the thermodynamic and ki
 netic parameters in the Markov state model are known. This knowledge enabl
 es a thorough analysis of the connection between the morphology of the fre
 e energy landscape and the folding dynamics of the protein-like chain.  \n
 \nNext\, it is shown how models of systems in which constituents interact 
 through continuous potentials can be used to develop discontinuous potenti
 al models through energy terracing.  This approach is demonstrated for a f
 luid system composed of interacting rigid bodies using the exact rotationa
 l motion of the rigid components.\n\nFinally\, a simple microscopic model 
 of chemically-powered Janus motors is presented in which motor interaction
 s with solvent particles occurs through hard collisions.  The spherical Ja
 nus particles\, consisting of catalytic and non-catalytic hemispheres\, pr
 oduce a gradient in concentration of chemical species that leads to self-g
 enerated diffusiophoretic motion.  The simple nature of the interactions e
 nables analytic expressions for the propulsion velocity as well as the con
 centration and fluid velocity fields to be obtained.  The analysis of the 
 emergent collective properties of the model from first principles provides
  a foundation from which the validity and limitations of approximate theor
 ies of the dynamics may be assessed.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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