p. 465 (Section 12.6.3) in Tuckerman's "Statistical Mechanics". There he talks about the path-integral generalization of the virial theorem, but the idea is pretty much the same. You have terms of the form ##x_k (\partial U / \partial x_k)## which are only valid for bound (not...
According to the virial theorem,
$$\left\langle T\right\rangle =-{\frac {1}{2}}\,\sum _{k=1}^{N}{\bigl \langle }\mathbf {F} _{k}\cdot \mathbf {r} _{k}{\bigr \rangle }$$
where ##N## is the number of particles in the system and ##T## is the total kinetic energy. It is often claimed that this...