Hellman-Feynman theorem relates the time derivative of energy in quantum mechanical system with the expectation value of the time derivative of the Hamiltonian operator.
It is a consequence of the variational principle, hence it is valid not only to true eigenstates but also for some other wave functions (e.g. Hartree-Fock) steming from the variational principle.
Historical references in physics are
H. Hellmann, Einfuehrung in die Quantenchemie (Franz Deuticke, Leipzig, 1937)
R. P. Feynman, Forces in molecules, Phys. Rev. 56, 340 (1939)
A strong version with careful functional analysis can be found in
The theorem also holds for the WKB approximations:
Created on May 26, 2015 at 10:41:37. See the history of this page for a list of all contributions to it.