Cleavage force, tribology and bond breaking in some transition metals
Faculty of Sciences. Physics
New York, N.Y.
The journal of physics and chemistry of solids. - New York, N.Y.
, p. 2055-2060
University of Antwerp
The idealised cleavage force F(z) as a function of interplanar separation z for Fe, Ni and Cu has been calculated using many-body interatomic potentials. The separation z, measured from the equilibrium cleavage planar separation a, at the maximum F(z)(max) is taken as a "criterion for bond breaking" and z(max) is found to be similar to0.2a for these metals. The results are also compared with earlier studies on covalently bonded Si and it is suggested that even in these metallic systems, cleavage may be associated with the breaking of bonds. The position of z(max) is found to depend on the number of broken bonds at the cleavage plane. From the results on Cu, it would appear that the main feature of F(z) is not very dependent on the form of the potential. For fixed cleavage separations, 0 < z < z > (max), energy curves are presented for the low velocity rubbing of two halves of a cleaved crystal in a parallel configuration, for non-defective solids. Bond breaking and bond bending aspects are discussed. It is concluded that bond charge or bond order force fields may be appropriate for describing the idealised tribology of the transition metals. The model presented should be viewed as a precursor, based on the assumption of ideal materials, to more realistic calculations of sliding adopting, for example, a dislocation mechanism. (C) 2000 Elsevier Science Ltd. All rights reserved.