Surface Energetics Classical Concepts

However, detailed knowledge about the dynamics of surface energetic identities is yet lacking [ 1,2,4], in particular, the atomistic and electronic origin, temperature and adsorbate dependence, and the analytical description of the interdependence between surface energetic identities and the energetically driven phenomena and processes. 

Usually, unrelaxed structmes at zero temperature are considered in the discussion of surface energies. The values obtained are then corrected for relaxations of the surface atoms, without mentioning reconstructions of the surface. In some cases, these corrections are thought very small, so a simplified model can be made without including relaxations. The temperatme dependence involves the phonons and their modification on the surface the vibrational effects sometimes have to be taken into account when the temperatme dependence is smdied. 

Galanakis et al. [9] correlated the surface energy of some d-metals to the broken bond in the tight-binding approximation. The is the number of d-electrons. Ws and Wb are the bandwidths for the surface and the bulk density of states, which took in rectangular forms. 

It has been found [16] that the stress in CrN films varies with film thickness, see Fig. 24.1, which corresponds to the sum of the tensile stress generated at the grain boundaries, compressive stress due to ion peening in deposition, and thermal stress due to the difference in thermal expansion between the coating and the substrate. 

The tensile part due to grain boundaries is thickness dependent. The other two contributions are thickness independent Sununation of the three components leads to a stress gradient in the coating. 

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The energy density gain and the cohesive energy remnant per discrete atom are suggested essential to classify the origin and temperature dependence of surface energetics and their responsibilities for surface processes and phenomena. These new concepts may provide a complementary to the classical theories of continuum medium mechanics and statistic thermodynamics. 

The basic theoretical concepts describing the interaction of a sufficiently massive and energetic particle with a surface are the binary collision (BC) model and the molecular or classical dynamics (MD) model. 

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