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- Summary
- Attempting a simplified but not-too-inaccurate intuitive description of van der Waals force.

When two atoms or molecules are brought within hailing distance of each other, their average internal charge distributions get modified because the electrons' state in molecule A is now a function of the field coming from molecule B, and vice versa. If, on an average, the electron distributions of A and B respond to each other's fields by shifting slightly to the left, we have an attractive force. The same would happen if both distributions shifted to the right.

However, this leads to the question, how do they "decide" to move to the left or to the right? In order to bring back some symmetry, there could be two ways of thinking:

[1] When the atoms begin to interact, there is an oscillation of the charge distribution along the line joining them. Since the oscillations in A and B are coupled via the field, they can well be correlated such that there is a net attractive force when averaged over time.

[2] The atoms, as a composite system, are in a superposition of "both left" and "both right", and the net force is attractive because both of these component states produces an attractive force.

My question is, [a] are the first two paragraphs a correct way of describing what's happening, and if so, which picture out of [1] and [2] is better?

(Or perhaps, are both 1 and 2 wide off the mark?)

[1] When the atoms begin to interact, there is an oscillation of the charge distribution along the line joining them. Since the oscillations in A and B are coupled via the field, they can well be correlated such that there is a net attractive force when averaged over time.

[2] The atoms, as a composite system, are in a superposition of "both left" and "both right", and the net force is attractive because both of these component states produces an attractive force.

My question is, [a] are the first two paragraphs a correct way of describing what's happening, and if so, which picture out of [1] and [2] is better?

(Or perhaps, are both 1 and 2 wide off the mark?)