Journal of Statistical Physics, Vol. 67, Nos. 1/2, 1992. p. 123-154.
The anisotropic interracial tension of the eight-vertex model is found by a new method, which introduces two inhomogeneous systems. As the width of the system becomes large, a doublet of the largest eigenvalues of the row-row transfer matrix is asymptotically degenerate. The anisotropic interracial tension is calculated from their finite-size correction terms in this limit. By the use of the anisotropic interracial tension, the equilibrium crystal shape of the eight-vertex model is derived via Wulff's construction. The equilibrium crystal shape is represented as a simple algebraic curve. We discuss the close relation between the algebraic curve and the form of an elliptic function appearing in the expression of the interracial tension.