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A network solid or covalent network solid (also called atomic crystalline solids or giant covalent structures) [1] [2] is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material.
Myoglobin sketch Alpha helix. 1958 – Myoglobin was the very first crystal structure of a protein molecule. [2] Myoglobin cradles an iron-containing heme group that reversibly binds oxygen for use in powering muscle fibers, and those first crystals were of myoglobin from the sperm whale, whose muscles need copious oxygen storage for deep dives.
It is an important property of typical molecular crystals with two or more symmetrically-equivalent molecules in the elementary cell, such as benzine and naphthalene, that their exciton absorption spectra consist of doublets (or multiplets) of bands strongly polarized along the crystal axes as was demonstrated by Antonina Prikhot'ko. This ...
A crystal's crystallographic forms are sets of possible faces of the crystal that are related by one of the symmetries of the crystal. For example, crystals of galena often take the shape of cubes, and the six faces of the cube belong to a crystallographic form that displays one of the symmetries of the isometric crystal system. Galena also ...
A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are termed shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they share electrons, is termed covalent bonding. [22]
Silicon crystallises in a giant covalent structure at standard conditions, specifically in a diamond cubic crystal lattice (space group 227). It thus has a high melting point of 1414 °C, as a lot of energy is required to break the strong covalent bonds and melt the solid.
Crystal structure of table salt (sodium in purple, chlorine in green). In crystallography, crystal structure is a description of ordered arrangement of atoms, ions, or molecules in a crystalline material. [1]
All phases of C 70 form brownish crystals with a bandgap of 1.77 eV; [2] they are n-type semiconductors where conductivity is attributed to oxygen diffusion into the solid from atmosphere. [13] The unit cell of fcc C 70 solid contains voids at 4 octahedral and 12 tetrahedral sites. [14] They are large enough to accommodate impurity atoms.