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An exciton is a bound state of an electron and an electron hole which are attracted to each other by the electrostatic Coulomb force resulting from their opposite charges. It is an electrically neutral quasiparticle regarded as an elementary excitation primarily in condensed matter, such as insulators, semiconductors, some metals, and in some liquids.
In chemistry, the lattice energy is the energy change upon formation of one mole of a crystalline ionic compound from its constituent ions, which are assumed to initially be in the gaseous state. It is a measure of the cohesive forces that bind ionic solids.
Lattice constants of atomic crystals are of the order of 1Å while those of superlattices (a) are several hundreds or thousands larger as dictated by technological limits (e.g. electron-beam lithography used for the patterning of the heterostructure surface). Energies are correspondingly smaller in superlattices.
A bound state is a composite of two or more fundamental building blocks, such as particles, atoms, or bodies, that behaves as a single object and in which energy is required to split them.
This example is readily extended to three dimensions, for example, to a body-centered cubic or face-centered cubic lattice by introducing the nearest neighbor vector locations in place of simply n a. [7] Likewise, the method can be extended to multiple bands using multiple different atomic orbitals at each site.
Peierls distortion of a 1-d periodic lattice. Imagine a lattice distortion where every other ion moves closer to one neighbor and further away from the other, the unfavourable energy of the long bond between ions is outweighed by the energy gain of the short bond. The period has just doubled from to .
Schematic picture of energy levels and examples of different states. Discrete spectrum states [nb 1] (green), resonant states (blue dotted line) [1] and bound states in the continuum (red). Partially reproduced from [2] and [3] A bound state in the continuum (BIC) is an eigenstate of some particular quantum system with the following properties:
Interstitial Atomic diffusion across a 4-coordinated lattice. Note that the atoms often block each other from moving to adjacent sites. As per Fick’s law, the net flux (or movement of atoms) is always in the opposite direction of the concentration gradient. H + ions diffusing in an O 2-lattice of superionic ice