THE MICROSCOPIC THEORY OF THE SURFACE-PROPERTIES OF ANHARMONIC CRYSTALS .2. THE (110) AND (111) SURFACE OF BCC CRYSTAL

The correlative unsymmetrized self-consistent field method developed in preceding works is used to study the structural, dynamical, and thermodynamic properties of the (110) and (111) faces of the anharmonic BCC crystal. The character of the lattice relaxation near the (110) surface is similar to that near the (001) face investigated in Part I. There is strong anisotropy in the atomic vibrations near the (110) surface and in its thermodynamic functions. Near the (111) face the lattice relaxation decreases gradually, with oscillations occurring in the interplanar distances. It should be emphasized that such results are obtained when the nearest-neighbour interactions are taken into account. Unlike the (001) face, the surface tensions of the faces considered are negative. The effect of the long-range interactions are studied. In the preceding papers1-7 the correlative unsymmetrized self-consistent field method (CUSF) has been developed to investigate the structural, dynamical, and thermodynamic surface properties of anharharmonic crystals. In the first part of this work7 (to be referred to as I), the (001) faces of BCC crystals have been studied taking into account the nearest-neighbour interactions. Here we shall calculate the properties of other singular surfaces of such crystals.