Wednesday, August 20, 2014
LiCN taking a dip in an Ar bath
A few years ago, my collaborators in Madrid and I found a reaction that seems to exhibit a rise and fall in chemical rates with increasing friction. (I wrote about one of my visits to my collaborators in Madrid in a previous post.) It involves the isomerization reaction from LiCN to CNLi where the lithium is initially bonded to the carbon, crosses a barrier and finally bonds to the nitrogen on the other side. We placed it inside an argon bath and used molecular dynamics to observe the rate. Our initial work fixed the CN bond length because that made the simulation much faster and we figured that the CN vibrational motion wouldn’t matter much. But the nagging concern that the CN motion might affect the results remained. So we went ahead and redid the calculations releasing the constraint on the CN motion. I’m happy to report that the rise and fall persisted. As such the LiCN isomerization reaction rate is fastest when the density of the Argon bath is neither too small nor too large, but rather when it is just right.
The article with my collaborators, Pablo Garcia Muller, Rosa Benito and Florentino Borondo was just published in the Journal of Chemical Physics 141, 074312 (2014), and may be found at this doi hyperlink. This work was funded by the NSF on the American side of the collaboration, by Ministry of Economy and Competiveness-Spain and ICMAT Severo Ochoa on the Spanish side, and by the EU’s Seventh Framework People Exchange programme.