For atoms or molecules, an electric dipole occurs where there is a separation of positive and negative charge over a short distance. For example, an electric dipole occurs for H2O where (the bent) molecule forms a small negative charge near the oxygen atom whereas an equal, but positive charge forms on the opposite side of the molecule associated with the hydrogen atoms.
The potential energy per unit of charge; the difference in electrical potential between two points is the voltage (V).
An electrode is a charged wire or plate. An anode is a positively charged electrode and a cathode is a negatively charged electrode. Charged particles are attracted to the electrode of opposite charge.
Electron tunneling is a quantum mechanical property that occurs because electrons behave as waves of energy and are thus capable of passing through an energy barrier that would not be possible in classical mechanics. In scanning tunneling microscopy (STM), the tip and sample wave functions overlap so that when a bias voltage is applied, there is some finite probability of finding the electron on the other side of the energy barrier. Depending upon the direction of the bias voltage in STM, an electron may jump the gap or ‘tunnel’ across the barrier from tip to sample or from sample to tip.
Electronegativity (electron affinity) is the ability for an atom to attract electrons. The original definition was specific to atoms, but it is often applied to functional groups, although reference to the dipole moment, polarity, and/or Lewis acid/base character may be more appropriate to describe the attraction of electrons within a particular molecule or bonding environment.
A constraint imposed on classical calculations or simulations of atomic structures in which the model system contains no net electric charge.
An obsolete term for allophane associated with lignite from Friesdorf, Germany.
In crystal nucleation theory, an incipient and metastable particle with a size smaller than a critical radius.
See critical radius
An obsolete term for margarite.
A mineral with a formula that is stoichiometric with respect to the asymmetric unit of the cell, and therefore reflects a lack of solid solution.
See solid solution for an example, also see asymmetric unit