Lennard Jones Potential

Lennard Jones Potential

The anti-symmetry of parallel spin electrons makes neutral atoms resist being pushed together.

The slight polarization of the electrons in one atom relative to another gives rise to a slight attraction between the atoms.

The potential between two neutral atoms can be written as[1]

Note that the potential minimum is at

On page 22 of Allen and Tildesley is the table

Atom	Source	ε/k (⁰K)	σ(nm)
H	Murad and Gubbins[2]	8.6	0.281
He	Maitland, et al[3]	10.2	0.228
C	Tildesley and Madden[4]	51.2	0.335
N	Cheung and Powles[5]	37.3	0.331
O	English and Venables[6]	61.6	0.295
F	Singer et al[7]	52.8	0.283
Ne	Maitland et al[8]	47.0	0.272
S	Tildesley and Madden	183.0	0.352
Cl	Singer et al	173.5	0.335
Ar	Maitland et al	119.8	0.341
Br	Singer et al	257.2	0.354
Kr	Maitland et al	164.0	0.383

While the above is valuable for working with real systems, for today

[1] M.P.Allen and D.J. Tildesley, Computer Simulation of Liquids, Oxford Science Publications, (1987,1989),p 9

[2] S.Murad and K.E. Gubbins, "Molecular dynamics simulation of methane using a singularity free algorithm". In Computer modelling of matter, (ed. P. Lykos) ACS Symposium Series Vol. 86, pp. 62-712. American Chemical Society, Washington.

[3] G.C. Maitland, et al, Intermolecular forces: their origin and determination, Clarendon Press, Oxford (1981)

[4] D.J. Tildesley and P.A. Madden, Mol. Phys. 42, 1137-1156 (1981)

[5] Mol. Phys. 30, 921-49 (1975)

[6] Proc. R. Soc. Lond. A340, 57-80 (1974)

[7] Mol. Phys. 33, 1757-95 (177)

[8] G.C. Maitland,M.Rigby,E.B.Smith,W.A. Wakeham, Intermolecular forces: their origin and determination, Clanendon, Oxford (1981)