Surface self-diffusion studies on the (111) surface of vanadium

The temperature dependence of the surface self-diffusion coeffiecient of vanadium was investigated experimentally under ultra-high vacuum conditions by using the sinusoidal profile decay technique. The rates of decay of profiles were measured in situ by using the laser diffraction technique. These diffusion studies were carried out on the (111) plane and the diffusion direction on this plane was controlled to be 〈2̄11〉. For the temperature range 1374–1521 K, the results were found to follow the relationship: $\text{D}{}_{\mathrm{<mtext>s</mtext><mtext>(111)</mtext>}}\text{〈}\text{2}\text{?}\text{11〉 = 66}\text{exp}\text{[?48,000)RT]}\text{cm}{}^2\text{/}\text{s}$. A comparison of activation energy with a pairwise potential model shows that a significant lattice relaxation is present when an atom occupies the saddle point configuration. Saddle point energies for various body centered cubic metals, calculated from the experimental data on surface diffusion, have been shown to vary linearly with the heat of vaporization.