atom is the smallest unit that consist of at least one atom.
smallest unit that consist of at least one atom?
atom
in his first extended published discussion of the atomic theory (1808), dalton proposed an additional (and controversial) "rule of greatest simplicity." this rule could not be independently confirmed, but some such assumption was necessary in order to propose formulas for a few simple molecules, upon which the calculation of atomic weights depended. this rule dictated that if the atoms of two different elements were known to form only a single compound, like hydrogen and oxygen forming water or hydrogen and nitrogen forming ammonia, the molecules of that compound shall be assumed to consist of one atom of each element. for elements that combined in multiple ratios, such as the then-known two oxides of carbon or the three oxides of nitrogen, their combinations were assumed to be the simplest ones possible. for example, if two such combinations are known, one must consist of an atom of each element, and the other must consist of one atom of one element and two atoms of the other.
john dalton
"polar optical:" the charge carrier exchanges energy with one of the polar optical modes of the crystal lattice. these modes are not present in covalent semiconductors. optical phonons arise from the vibration against each other of atoms of different types when there is more than one atom in the smallest unit cell, and are usually excited by light.









































"non-polar optical:" energy is exchanged with an optical mode. non-polar optical phonons must generally be considered in covalent semiconductors and the l-valley of gaas.
monte carlo methods for electron transport