Wiktionary
n. A small crystal from which a larger crystal of the same substance is grown
Wikipedia
A seed crystal is a small piece of single crystal / polycrystal material from which a large crystal of the same material typically is to be grown. The large crystal can be grown by dipping the seed into a supersaturated solution, into molten material that is then cooled, or by growth on the seed face by passing vapor of the material to be grown over it.
The theory behind this effect is thought to derive from the physical intermolecular interaction that occurs between compounds in a supersaturated solution (or possibly vapor). In solution, liberated (soluble) molecules ( solute) are free to move about in random flow. This random flow permits for the possibility of two or more molecular compounds to interact. This interaction can potentiate intermolecular forces between the separate molecules and form a basis for a crystal lattice. The placement of a seed crystal into solution allows the recrystallization process to expedite by eliminating the need for random molecular collision / interaction. By introducing an already pre-formed basis of the target crystal to act upon, the intermolecular interactions are formed much more easily / readily than relying on random flow. Often, this phase transition from solute in a solution to a crystal lattice will be referred to as nucleation. Seeding is therefore said to decrease the necessary amount of time needed for nucleation to occur in a recrystallization process.
One example where a seed crystal is used to grow large boules or ingots of a single crystal is the semiconductor industry where methods such as the Czochralski process or Bridgman technique are employed.
Usage examples of "seed crystal".
In some crystals with large periods (as many as a thousand atoms), it has been discovered that in order for growth to occur, the seed crystal must contain a dislocation, usually a screw dislocation.
These have grown from a seed crystal in the soil, drawing their substance from the dissolved minerals in water.
Starting with the core group of coveners and friends who'd gathered at her cabin days after the Change, and out from there as they took in refugees-One recently retired English soldier caught out on a hunting trip, for instance-and then became the seed crystal of order and survival in this corner of the Valley.
The cult virus had linked individual lives around the seed crystal of a charismatic, drawing the inhabitants of each star system into a single, sublime entity of many parts.
In the century after the Fall, remnants of FORCE had formed a vicious military dictatorship -- the so-called Martian War Machine -- which extended its rule as far as the Centauri and Tau Ceti systems and might well have become the seed crystal for a second interstellar empire if the Pax had not arrived, quickly subduing the Martian fleets, driving the War Machine back to Old Earth System, sending the dispossessed warlords into hiding among the ruins of FORCE orbital bases and in the old tunnels under Mons Olympus, replacing the War Machine's presence in Old Earth System with Pax Fleet bases in the asteroid belt and among the Jovian moons, and finally sending missionaries and Pax governors to pacified Mars.
In every situation, there can be a seed crystal of goodness and decency, of sensibility.
Then you came, a seed crystal, and immediately the pattern was broken.
But once that last clause no longer obtained, once world hunger and the arms race and death and pain themselves were seen to be soluble problems, humanity leaped to embrace telepathy with such ardor that it was as though Jacques LeBlanc's golden crown had been a seed crystal dropped into the heart of a great supersaturated solution, which collapsed at once into a structure, a pattern, of awesome complexity and beauty.
The spell had fallen into the molten metal like a seed crystal into the alum-water that the dyers used, and from it structure had feathered out like frost, intricate and beautiful.