Diamond crystal growth mystery

In the equilibrium environment of nature, the formation of most crystals and their growth and change require a long geological history. But under laboratory conditions, the time scale for crystal formation and growth can be greatly shortened. This is of course the artificial conditions changed the growth environment of the crystal, but it is also not unrelated to the reason of the crystal itself. Therefore, understanding and studying the crystal formation process and some phenomena in the crystal growth process is a basic content of crystallography.

The process of crystal formation is the process of material changing from other phases to crystalline phases. That is, the process by which the original amorphous substance is transformed into a crystalline substance under certain physical and chemical conditions (temperature, pressure and component concentration, etc.). The main ways of crystal formation are:

01 is crystallized by gas

A gas at its supersaturated vapor pressure or supercooling temperature directly changes from the gas phase to a crystal. The most typical example in life is the ice flower, the ice flower on the window in winter is the result of direct crystallization of water vapor in the air.

02 Crystallized in a liquid (solution or molten body)

If the sea water evaporates, the solution reaches supersaturation and crystallizes out stone salt. The magma melt inside the crust forms crystals such as feldspar and quartz during the cooling process.

03 From solid phase to crystal

This phase transition can also take two forms:

(1) Under the same temperature and pressure conditions, the amorphous body of a substance is transformed into crystalline body. Because an amorphous body has a larger free energy than a crystal, it can spontaneously transition to a crystalline body with a smaller free energy. Such as graphite products have amorphous coke, asphalt, etc., after high temperature action to form graphite crystals.

(2) from one crystalline phase to another crystalline phase. This phase transition is often referred to as a homogeneous multiimage transition. Synthetic diamond, for example, is usually converted from graphite under high temperature and extreme pressure.