# Atomic electric dipole moment

1. Aug 27, 2007

### malawi_glenn

Hi I was wondering if anyone could give me info about atomic electric dipole moment at a very fundemental level (fenomenological, basic quantum), I do not seem to find it when I google =(

My Aim is just to understand van der Waals binding in solids a little bit more.

2. Aug 27, 2007

### olgranpappy

There's a short section about the physical origin of the van der Waals "Fluctuating dipole" forces on page 390 of Ashcroft and Mermin "Solid State Physics". It is a very short section though.

Also, Chaikin and Lubensky section 1.3.2 on van der Waals is good. Basically, they expand the Hamiltonian for two atoms (electrons and nuclei, whose nuclei are a fixed distance R apart) and do perturbation theory using

$$H' = \frac{e^2}{R^3}(x^1x^2+y^1y^2-2z^1z^2)$$

the first order perturbation vanishes and they have to go to second order (thus we see that the perturbation of the energy goes like 1/R^6).

Actually working out the matrix elements is a little painful even in the case of H atoms, but it can be done in that case.

3. Aug 27, 2007

### malawi_glenn

Thanks, I'll check out the library