Transitions into, and out of intermediate phases (IPs) with minimal strain have been identified to date by Boolchand and co-workers, in bulk glasses, primarily by the extraordinary low values of the change in enthalpy, ΔH nr , associated with non-reversible heat flow, and by Lucovsky and coworkers in deposited thin films, and at dielectric–semiconductor interfaces by combining spectrographic characterizations, primarily synchrotron X-ray absorption and X-ray photoemission, and electrical measurements. This paper emphasizes chemical bonding self-organizations that minimize macroscopic strain within the IP windows, and identifies for the first time the necessary and sufficient conditions for IP windows to open, and to close, as a function of changes in the alloy composition. Percolation theory, and in particular competitive and synergistic double percolation provide a quantification of IP window first and second transition compositions that account for many of the experimentally determined IP window threshold transitions and IP window widths identified to date.