Abstract
Recent analytical methods to determine the equilibrium form of crystals are reviewed. Yamada's contribution for a terrace ledge kink (TLK) model is presented. The step density on a vicinal face, which is introduced by him, is related to the orientation |p| of the surface. The concept of the projected surface free energy density β is also introduced by Yamada. Step energy and interaction between steps are considered to the calculation of the projected surface free energy density. Andreev's Legendre-transformed surface free energy density gives the shape of equilibrium form. Garcia, Saenz and Cabrera racognized the idea of Legendre transformation independently. Cabrera's expansion of β by |p| is used to determine the equilibrium form of α-Ag_2S by using the Legendre transformation of crystal shape.
