# Lennard-Jones potential - equilibrium [closed]

If I have Lennard-Jones potential, how can I calculate equilibrium? $$U(r)=\epsilon \left ( \left (\frac{r_m}{r} \right )^{12}-2 \left (\frac{r_m}{r}\right )^6 \right ) \$$

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## closed as too localized by dmckee♦May 6 '13 at 2:10

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-Is this a HW question by chance? We don't usually solve HW questions here. If you want a hint, I would sketch a plot of the potential. Particular points should jump out as candidates for an equilibrium positions - if recall your calculus class there is a way to find said points... – DJBunk Jul 11 '12 at 21:25
Equilbrium of what? Two atoms? Temperature? Zero temperature? Many atoms? fluid? gas? This is not a question as it stands. – Ron Maimon Jul 12 '12 at 1:45
$\vec F = -{d U \over dr } = 0$ – Santosh Linkha Jul 12 '12 at 2:59

A hint: The derivative of a potential energy such as $U$ is, with suitable sign, a force. At equilibrium what should the force be?