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Phase transitions (phase changes) that help describe polymorphism include polymorphic transitions as well as melting and vaporization transitions. According to IUPAC, a polymorphic transition is "A reversible transition of a solid crystalline phase at a certain temperature and pressure (the inversion point) to another phase of the same chemical composition with a different crystal structure."
Dislocation creep is a non-linear (plastic) deformation mechanism in which vacancies in the crystal glide and climb past obstruction sites within the crystal lattice. [1] These migrations within the crystal lattice can occur in one or more directions and are triggered by the effects of increased differential stress.
Isomorphous compounds give rise to isomorphous crystals and form solid solutions. [2] Historically, crystal shape was defined by measuring the angles between crystal faces with a goniometer . Whereas crystals of Fe(acac) 3 are deep red and crystals of Al(acac) 3 are colorless, a solid solution of the two, i.e. Fe 1−x Al x (acac) 3 will be ...
In addition, physical properties are often controlled by crystalline defects. The understanding of crystal structures is an important prerequisite for understanding crystallographic defects. Most materials do not occur as a single crystal, but are poly-crystalline in nature (they exist as an aggregate of small crystals with different orientations).
Both the resultant crystalline mosaics and/or polymorphs are chemically identical—with a few minor exceptions due to certain relatively minute chemical alterations that occur during the reaction processes—to the minerals from which the aggraded crystals developed. [4] One common form of aggrading neomorphism is called porphyroid neomorphism.
The minerals present in the rock often do not reflect conditions of chemical equilibrium, and the textures produced by dynamic metamorphism are more significant than the mineral makeup. [ 65 ] There are three deformation mechanisms by which rock is mechanically deformed.
Minerals bond grains of sediment together by growing around them. This process is called cementation and is a part of the rock cycle. Cementation involves ions carried in groundwater chemically precipitating to form new crystalline material between sedimentary grains. The new pore-filling minerals form "bridges" between original sediment grains ...
The types and abundance of minerals in a rock are determined by the manner in which it was formed. Most rocks contain silicate minerals, compounds that include silica tetrahedra in their crystal lattice, and account for about one-third of all known mineral species and about 95% of the earth's crust. [6] The proportion of silica in rocks and ...