ABSTRACT
The validity of the virial theorem was proved by Born, Heisenberg and Jordan1 on the ground of matrix calculation and after that by Finkelstein2 on the ground of the Schro¨dinger equation. Both proofs essentially reproduced ideas of the classical approach. In the present note, a new and purely quantum mechanical derivation of this relation is given from the variational principle. The derivation is very simple and allows one to get some interesting consequences.
