The most common lattice structures for metals are those obtained by stacking the atomic spheres into the most compact arrangement. There are two such possible periodic arrangements. In each, the first layer has the atoms packed into a plane-triangular lattice in which every atom has six immediate neighbours.…

…in successful epitaxy is matching lattice distances. If the spacing between atoms in the substrate is close to that of the top crystal, then that crystal will grow well; a small difference in lattice distance can be accommodated as the top crystal grows. When the lattice distances are different, however,…

…pattern of atoms in their crystals), with eight nearest neighbours to each atom. The closest distance between atoms, a characteristic property of crystals, increases with increasing atomic weight of the alkali metal atoms. As a group, the alkali metals have a looser crystallographic arrangement than any of the other metallic…

…so, they migrate within the lattice, more rapidly at higher temperatures. Sometimes they do not reach the usual arrangement of two hydrogen atoms connected by covalent bonds to each oxygen atom, so that some oxygen atoms have only one or as many as three hydrogen bonds. Such oxygen atoms become…

…is, it consists of many crystals that join one another on their boundaries. A crystal is a well-ordered arrangement of atoms that can best be pictured as spheres touching one another. They are ordered in planes, called lattices, which penetrate one another in specific ways. For iron, the lattice arrangement…

…in many cases, the metallic crystal lattice merely expands to accommodate the dissolved hydrogen without any other change.

Semiconductor crystals such as silicon or germanium are used as X-ray detectors in the range from 1,000 electron volts (1 keV) to more than 1 MeV. An X-ray photon absorbed by the material excites a number of electrons from its valence band to the conduction band.…

…to specific sites in the crystalline lattice and are said to have an energy in the valence band. At any given time, a few electrons will have gained sufficient thermal energy to have broken loose from localized sites and are called conduction electrons; their energy lies in a higher conduction…

…spacing of atomic planes in crystals and the angles of incidence at which these planes produce the most intense reflections of electromagnetic radiations, such as X-rays and gamma rays, and particle waves, such as those associated with electrons and neutrons. For maximum intensity of reflected wave trains, they must stay…

…arrangement of atoms in a crystal. Each point represents one or more atoms in the actual crystal, and if the points are connected by lines, a crystal lattice is formed; the lattice is divided into a number of identical blocks, or unit cells, characteristic of the Bravais lattices. The French…

…connected by lines, the resulting lattice may be divided into a number of identical blocks, or unit cells; the intersecting edges of one of the unit cells defines a set of crystallographic axes, and the Miller indices are determined by the intersection of the plane with these axes. The reciprocals…

…broadly into the categories of lattice dynamics and hyperfine interactions, although contributions have been made in other areas. The probability that a gamma-ray emission process will be recoil free depends on the amplitude of the thermal vibrations compared to the wavelength of the gamma ray. A measurement of the fraction…

…on the effect of the crystal lattice on the magnetic centre under study. The effect of the crystal field, particularly if it has little symmetry, is to reduce the magnetism caused by orbital motion. To some extent the orbital magnetism is preserved against ligand fields of low symmetry by the…

…displacements of ions in the crystal lattice. Such an effect is not found in crystals with a centre of symmetry. The direct effect can be quite strong; a potential V = Y_edδ/ε₀K is generated in a crystal compressed by an amount δ, where K is the dielectric constant. If lead…

In neutron irradiation of a solid, atoms are dislodged from normal lattice positions and set in motion (the Wigner effect). The fractional amount of energy transfer depends, as in any elastic collision, on the mass ratio of the neutron to that of the…

crystallography, fundamental property of the orderly arrangements of atoms found in crystalline solids. Each arrangement of atoms has a certain number of elements of symmetry; i.e., changes in the orientation of the arrangement of atoms seem to leave the atoms unmoved. One such element of…

…structures to which a given crystalline solid can be assigned. Components of crystals in this system are located by reference to four axes—three of equal length set at 120° to one another and a fourth axis perpendicular to the plane of the other three. If the atoms or atomic groups…

>crystal systems to which a given crystalline solid can be assigned. Crystals in this system are referred to three mutually perpendicular axes of equal lengths. If the atoms or atom groups in the solid are represented by points and the points are connected, the resulting…

…the structural categories to which crystalline solids can be assigned. Crystals in this system are referred to three axes of unequal lengths—say, a, b, and c—of which a is perpendicular to b and c, but b and c are not perpendicular to each other.

…structural categories systems to which crystalline solids can be assigned. Crystals in this system are referred to three mutually perpendicular axes that are unequal in length.

…the structural categories to which crystalline solids can be assigned. Crystals in this system are referred to three axes of unequal lengths that are inclined at nonorthogonal (nonperpendicular) angles relative to each other.

…the structural categories to which crystalline solids can be assigned. The trigonal system is sometimes considered to be a subdivision of the hexagonal system.