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Merohedral twinning occurs when the lattices of the contact twins superimpose in three dimensions, such as by relative rotation of one twin from the other. [8] An example is metazeunerite. [9] Contact twinning characteristically creates reentrant faces where faces of the crystal segments meet on the contact plane at an angle greater than 180°. [3]
The contact goniometer was the first instrument used to measure the interfacial angles of crystals. The International Union of Crystallography (IUCr) gives the following definition: "The law of the constancy of interfacial angles (or 'first law of crystallography') states that the angles between the crystal faces of a given species are constant, whatever the lateral extension of these faces ...
The evolutionary origin of birds was an open question in paleontology for over a century, but the modern scientific consensus is that birds evolved from small feathered theropods in the Jurassic. Not all dinosaur lineages were cut short at the end of the Cretaceous during the Cretaceous–Paleogene extinction event , and over 11,000 species of ...
Electron microscopy of antisites (a, Mo substitutes for S) and vacancies (b, missing S atoms) in a monolayer of molybdenum disulfide.Scale bar: 1 nm. [1]A crystallographic defect is an interruption of the regular patterns of arrangement of atoms or molecules in crystalline solids.
Mineralogy applies principles of chemistry, geology, physics and materials science to the study of minerals. Mineralogy [n 1] is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts.
A: Space-Group Symmetry, [2] and the data of maximal subgroups of space groups as listed in International Tables of Crystallography, Vol. A1: Symmetry relations between space groups. [3] A k-vector database with Brillouin zone figures and classification tables of the k-vectors for space groups is also available via the KVEC tool.
Pericline also refers to a doubly plunging anticline or syncline.. Pericline is a form of albite exhibiting elongate prismatic crystals. [1]Pericline twinning is a type of crystal twinning which show fine parallel twin laminae typically found in the alkali feldspars microcline. [2]
In crystallography, mosaicity is a measure of the spread of crystal plane orientations. A mosaic crystal is an idealized model of an imperfect crystal, imagined to consist of numerous small perfect crystals (crystallites) that are to some extent randomly misoriented.