Recent research results have suggested that double percolation processes play a significantrole in the formation of intermediate phases (IPs) in non-crystalline thin films. Oneclass of IP windows, involving competitive double percolation, occurs in binaryAsxSe1−x andGexSe1−x alloys and in thepseudo-binary AsxGexSe1−2x alloy. This IP window occurs over an 8–12% composition range. Transitions that define theIP window in the Ge–Se alloys involve a competition between the elimination of compliantlocal bonding dimer groups, e.g. Ge–Se–Se–Ge, at the expense of an increasing fraction ofrigid local bonding monomer groups, e.g. Ge–Se–Ge. Compliant monomer groupbonding defines the first window transition for an average number of bondingconstraints/atom,nc = 3; the second transition from rigid to stressed rigid occurs when the compliantmonomer concentration drops below a concentration for percolation.A second class of IPs with significantly narrower composition windows,∼1 to atmost 3%, is proposed to explain experimentally determined IPs in chalcogenide alloys with halogen dopants;e.g. a-Ge0.25Se0.77−xIx, where the IPwindow width is ∼1%. We suggest that this narrow window is determined by a confluent coherent doublepercolation process that includes (i) broken bond-bending constraints that minimize localbond strain, and (ii) a percolation pathway based on a second and complementary localbonding group. However, this second class of IPs is not supported by theory and modelingas yet, and as such our designation of this class of IPs must be regarded as morespeculative. On the other had, it is significant that at least two other alloy systems,Ge2Se2Te5 and pseudo-ternary Hf, Zr and Ti Si oxynitrides, display narrow regimes where bondconstraint counting indicates local strain suppression, and where a second and largerbonding arrangement is present at the percolation limit.