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The dividing line between metals and nonmetals can be found, in varying configurations, on some representations of the periodic table of the elements (see mini-example, right). Elements to the lower left of the line generally display increasing metallic behaviour; elements to the upper right display increasing nonmetallic behaviour.
Schematic representations of a tilt boundary (top) and a twist boundary between two idealised grains. The simplest boundary is that of a tilt boundary where the rotation axis is parallel to the boundary plane. This boundary can be conceived as forming from a single, contiguous crystallite or grain which is gradually bent by some external force ...
The LeRoy radius, derived by Robert J. LeRoy, defines the internuclear distance between two atoms at which LeRoy-Bernstein theory (sometimes called near-dissociation theory) becomes valid. LeRoy-Bernstein theory is a semi-classical ( WKB ) approach for describing vibrational energy levels near the molecular dissociation limit. [ 1 ]
A grain boundary is a single-phase interface, with crystals on each side of the boundary being identical except in orientation. The term "crystallite boundary" is sometimes, though rarely, used. Grain boundary areas contain those atoms that have been perturbed from their original lattice sites, dislocations , and impurities that have migrated ...
Initially, one line (representing a single bond) is drawn between each pair of connected atoms. Each bond consists of a pair of electrons, so if t is the total number of electrons to be placed and n is the number of single bonds just drawn, t−2n electrons remain to be placed. These are temporarily drawn as dots, one per electron, to a maximum ...
Covalent radius: the nominal radius of the atoms of an element when covalently bound to other atoms, as deduced from the separation between the atomic nuclei in molecules. In principle, the distance between two atoms that are bound to each other in a molecule (the length of that covalent bond) should equal the sum of their covalent radii. [13]
Dislocations can move if the atoms from one of the surrounding planes break their bonds and rebond with the atoms at the terminating edge. It is the presence of dislocations and their ability to readily move (and interact) under the influence of stresses induced by external loads that leads to the characteristic malleability of metallic materials.
A boundary point of a set is any element of that set's boundary. The boundary ∂ X S {\displaystyle \partial _{X}S} defined above is sometimes called the set's topological boundary to distinguish it from other similarly named notions such as the boundary of a manifold with boundary or the boundary of a manifold with corners , to name just a ...