External field as a tool for measuring absolute values of step-step interaction

In absence of any external field, the equilibrium profile z(x) of a vicinal rounded part tangentially joined to a flat facet is known to follow a universal scaling law z(x) ∝ x3/2. This universal behaviour is modified when the crystal is plunged in an external field. The deviation from the universal Gruber-Mullins-Pokrovsky-Talapov behaviour depends on the facet orientation, the chemical potential of the crystal and the external field. We show that measuring this deviation is enough to provide absolute value of the step-step interaction. Applications to gravitation and centrifugation fields are discussed.