Lennard-Jonesgreenspun.com : LUSENET : UR General Chemistry : One Thread
What is the Lennard-Jones equation? It is not showing up on the course notes. What is it used for?
-- Anonymous, April 30, 2000
The Lennard Jones potential is a curve showing the potential energy as a function of distance.
there are different models which enable one to look at the potential energy of different systems--there are the couloumbic potential and the lennard-jones potential just to name two of many.
look at figure 13.1 in your text--this is an example of the coulombic potential...the lennard-jones potential energy surface plot would look a lot like this one (exactly like this one actually if you look into generalities....the line shape on a plot of energy vs distance.) The reason one would use different models is because there are many different systems one could look at and many different questions one wishes to answer. Some models would represent the system better than others...a model with more detail is required to fit molecular beam scattering experiments than is required for viscosity for instance.
I would say you should know what one of these plots looks like and what it shows...hence the reference to the text and the coulombic plot in fig 13.1. Some questions you could ask yourself when you look at the plot....where is the energy the lowest??? why??? what is happening at other points on the line???
I am not sure how much you need to know on this, but I am sure you don't need to know that the l-j potential curve is given by V(r) = 4e [(s/r)^12 - (s/r)^6] but there it is. I found this in a text by Steinfeld Francisco and Hase entitled Chemical Kinetics and Dynamics (2nd ed.)
-- Anonymous, May 01, 2000