The most common application of the Hellmann–Feynman theorem is the calculation of intramolecular forces in molecules. This allows for the calculation of equilibrium geometries – the nuclear coordinates where the forces acting upon the nuclei, due to the electrons and other nuclei, vanish. The parameter λ λ corresponds to the coordinates of the nuclei. For a molecule with 1 ≤ ≤ i ≤ ≤ N electrons with coordinates { r i } , and 1 ≤ ≤ α α ≤ ≤ M nuclei, each located at a specified point { R α α = { X α α , Y α α , Z α α } } and with nuclear charge Z α α , the clamped nucleus Hamiltonian is