In the lectures, which said ’ Because we consider a 3D solid, each atom contains 3 spatial and 3 momentum degrees of freedom. Therefore, the total heat capacity per atom is C=3kB’
how to understand momentum is degrees of freedom？ Does it in phase space?
why ideal gas don’t have momentum degrees of freedom?
Thank you!
A degree of freedom is any momentum or coordinate that enters the energy quadratically. So in an ideal gas each of the 3 components of momentum gives kT/2, and in a harmonic oscillator so do coordinates. This is explained in more detail in the equipartition theorem.
Thank you, Anton. Nice answers which is extremely helpful for me.