Special MS&E Colloquium with Dr. Robin Hayes
Date: March 03, 2008 from 10:00 am to 4:00 pm EST
Location: 214 S. W. Mudd
Contact: For further information regarding this event, please contact Chad Gurley by sending email to cg2029@columbia.edu .
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"Nanostructured Materials Design from First Principles: Where Chemistry Meets Engineering"

Dr. Robin Hayes, New York University

Chemistry at the atomic scale can have profound effects on macroscopic behavior.  The ability to directly probe nanoscale phenomena via first principles methods opens up the possibility to design nanostructured materials without relying upon empirical parameters.  Two examples, patterned organic-semiconductor interfaces and proton transport in polymer electrolyte membranes (PEM), will be discussed.  Self-assembled interfaces between small organic molecules and semiconductor surfaces promise to unite the rich variety of bio/organic functionality with the established semiconducting infrastructure to yield novel applications in molecular computing, nanolithography, and chemical and biological sensors.  Design principles, including structural and kinetic effects, are gleaned from ab initio molecular dynamics simulations of cyclohexadiene reacting with Si(100)-2x1 and SiC(001)-3x2 surfaces (Figure A).  A surprising attraction between C=C moieties and subdimer sites on the SiC(001)-3x2 surface alters the expected product distribution, creates a subsurface defect, and destroys the well-ordered hybrid interface.  Likewise, first principles methods are often necessary to capture the bond breaking and forming events that occur during proton transport.  Nafion, the material of choice in PEM fuel cells, suffers from low proton diffusion upon loss of hydration.  Ab inito molecular dynamics of trifluoromethanesulphonic acid hydrates provide insights into proton transport mechanisms in Nafion in the low hydration regime (Figure B).  Preliminary results reveal the prevalence of Grottus-type "proton hopping" transport mechanisms and the drive for protons to be fully hydrated.