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D.V. Kalinin, S.V. Vosel, V.V. Serdobintseva
The paper presents a new view of microstructure of precious opals. Precious opals are considered to be gel crystals in which supermolecular monodisperse spheres of amorphous silica (MSS) serve as structural units of the crystal lattice. Formation of opal structure is a kind of crystallization or a phase transition of first type. Based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, potential energy curves for interaction in a couple of MSS are considered. As a result of this interaction, the particles are fixed first at some space apart (structures I) and then come into immediate contact (structures II). External factors that cause crystallization of concentrated particle suspensions are discussed.