Lennard Jones Potential

Lennard Jones Potential#

The Lennard-Jones 6-12 potential energy, which describes the potential energy between neutral gases, is u(r)=u0(r0r)12−2(r0r)6, where r is the separation between atoms. For Ar, r0=3.9×10−10 m and u0=1.6×10−21 J (according to D. V. Schroeder, An Introduction to Thermal Physics).

Part 1#

Roughly sketch the form of the potential energy as a function of r. On your diagram indicate the value of r and u at the minimum energy in terms of r0 and u0 (note: dudr=0 at this point). Also indicate where the potential energy starts to become positive, and its behavior as r→∞.

upload your work as a png file named ‘potential’.

Answer Section#

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Part 2#

Derive an expression for the force between the atoms as a function of r.

On your diagram from part 1 above, label the regions where the force is negative (attractive) between atoms, and where the force is positive (repulsive) between atoms.

For

Use

ro

R

r

r

uo

u

Answer Section#

Attribution#

Problem is licensed under the CC-BY-NC-SA 4.0 license.
The Creative Commons 4.0 license requiring attribution-BY, non-commercial-NC, and share-alike-SA license.