Solid symmetry dividing plane

Figure 4.11 Definition of the solid angle fi0 of a point source Q accepted by the entrance slit S of a sector CMA. Two cross-cuts are shown (a) for a plane containing the symmetry axis of the analyser, (b) for a plane perpendicular to this axis. The principal ray starting at Q is shown together with the angular spreads from the finite acceptances in A and Acp. If expressed in spherical coordinates, the slit S has a width b = r2 A and a length i = i ,2 + A

There are a number of band-structure methods that make varying approximations in the solution of the Kohn-Sham equations. They are described in detail by Godwal et al. (1983) and Srivastava and Weaire (1987), and we shall discuss them only briefly. For each method, one must eon-struct Bloch functions delocalized by symmetry over all the unit cells of the solid. The methods may be conveniently divided into (1) pesudopo-tential methods, (2) linear combination of atomic orbital (LCAO) methods (3) muffin-tin methods, and (4) linear band-structure methods. The pseudopotential method is described in detail by Yin and Cohen (1982) the linear muffin-tin orbital method (LMTO) is described by Skriver (1984) the most advanced of the linear methods, the full-potential linearized augmented-plane-wave (FLAPW) method, is described by Jansen... 

The concepts of crystalline state and symmetry are just about synonymous today, although the general sense of symmetry is much older than the idea of symmetrical arrangement of atoms in the structures of crystalline solids. Following Webster s dictionary, symmetry is the beauty of form arising from balanced proportions , and to be symmetrical is to have the correspondence in size, shape and relative position or parts on opposite sides of a dividing line or median plane or about a center or axis . 

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