# Degrees of freedom of an oscillator in an Einstein solid

1. Jun 14, 2012

### PhysicsGirl90

I was reading through a book on statistical physics when i came across this sentence: "An Einstein solid has two degrees of freedom for every oscillator."

How is this possible? I picture an oscillator (ex. mass on spring) to move only in one dimension, thus one degree of freedom. Where does the second degree of freedom come from?

2. Jun 14, 2012

### M Quack

http://en.wikipedia.org/wiki/Einstein_solid

I am actually puzzled why there are 2 degrees of freedom, and not 3.

There are many ways to picture an oscillator.

A mass on a spring is good for 1D, but you can generalize that also to more dimensions:

Put the mass in the center of a square and attach 4 identical springs from the corners to the mass. Now the mass can oscillate in two directions. do the same with an octahedron, and the mass can oscillate in 3 directions.

A crystal corresponds best to this last case. Just instead of springs you have electric potentials (and a load of QM effects).