In crystallography, the orthorhombiccrystal system is one of the 7 lattice point groups. Orthorhombic lattices result from stretching a cubic lattice along two of its lattice vectors by two different factors, resulting in a rectangular prism with a rectangular base (a by b, which is different from a) and height (c, which is different from a and b). The three lattice vectors remain mutually orthogonal.
There are four orthorhombic Bravais lattices: simple orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic.
simple orthorhombic
base-centered orthorhombic
body-centered orthorhombic
face-centered orthorhombic
The point groups (or crystal classes) that fall under this crystal system are listed below, followed by their representations in international notation and Schoenflies notation, and mineral examples.
The invention relates to orthorhombic greenish-tinged lead chromate pigments containing lead chromate and lead sulfate in a weight ratio of 91:9 to 100:0, which are distinguished by a very high tinctorial strength in application.
Orthorhombic lead chromate pigments in which the weight ratio of lead chromate to lead sulfate is 94:6 to 98:2 are preferred.
The orthorhombic lead chromate pigments obtained can additionally be treated with agents to improve their texture, for example with long-chain aliphatic alcohols, esters, acids or salts thereof, amines, amides, waxes or resinous substances, such as abietic acid or hydrogenation products, esters or salts thereof, and furthermore with nonionic, anionic or cationic surface-active organic agents.
is found to exhibit extremely unusual features which include pressure independence of the Curie temperature in the orthorhombic phase, a re-entrance of the rhombohedral phase at low temperatures, and a change of the type of the magnetic phase transition from second to first-order at the intersection of the structural and magnetic phase boundaries.
The orthorhombic (2 0 0) and (4 0 5) reflections were chosen to monitor the magnetic and structural phase-transitions, respectively.
When the crystal is compressed in the orthorhombic phase, the Mn-O-Mn angle is 180° by symmetry, and pressure cannot affect it, changing instead the inter-planar distances.
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