Should All Crystals Be bcc? Landau Theory of Solidification and Crystal Nucleation

Very general symmetry considerations uniquely favor a bcc crystal structure near the melting line. This agrees with observations that almost all metals on the left-hand side of the periodic table are bcc at high temperature, and that, even where other structures are more stable, the first phase nucleated on rapid cooling can be bcc. Furthermore, icosahedral local symmetries are favored in amorphous solids. Fluctuation effects cause the transition from isotropic liquid to crystal to be first order in any dimension.