Lithium Lithium Lithium (from ) is a chemical element with symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. When cut, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals which were once the main source of lithium. Due to its solubility
Helical boundary conditions one coordinate to describe arbitrary-dimensional lattices. Helical boundary conditions In mathematics, helical boundary conditions are a variation on periodic boundary conditions. Helical boundary conditions provide a method for determining the index of a lattice site's neighbours when each lattice site is indexed by just a single coordinate. On a lattice of dimension "d" where the lattice sites are numbered from 1 to "N" and "L" is the width (i.e. number of elements per row) of the lattice in all but the last dimension, the neighbors of site "i" are: It is not necessary that "N" = "L". Helical boundary conditions