Self-diffusion of adatoms, dimers, and vacancies on Cu(100)

We use ab initio static relaxation methods and semi-empirical molecular-dynamics simulations to investigate the energetics and dynamics of the diffusion of adatoms, dimers, and vacancies on Cu(100). It is found that the dynamical energy barriers for diffusion are well approximated by the static, 0 K barriers and that prefactors do not depend sensitively on the species undergoing diffusion. The ab initio barriers are observed to be significantly lower when calculated within the generalized-gradient approximation (GGA) rather than in the local-density approximation (LDA). Our calculations predict that surface diffusion should proceed primarily via the diffusion of vacancies. Adatoms are found to migrate most easily via a jump mechanism. This is the case, also, of dimers, even though the corresponding barrier is slightly larger than it is for adatoms. We observe, further, that dimers diffuse more readily than they can dissociate. Our results are discussed in the context of recent submonolayer growth experiments of Cu(100).Comment: Submitted to the Physical Review B; 15 pages including postscript figures; see also http://www.centrcn.umontreal.ca/~lewi

One-dimensional nanoclustering of the Cu(100) surface under CO gas in the mbar pressure range

The bulk terminated Cu(100) surface becomes unstable in the presence of CO at room temperature when the pressure reaches thembar range. Scanning tunneling microscopy images showthat above 0.25mbar the surface forms nanoclusters with CO attached to peripheral Cu atoms. At 20 mbar and above 3-atom wide one- dimensional nanoclusters parallel to b001N directions cover the surface,with CO on every Cu atom, increasing in density up to 115 mbar. Density functional theory explains the findings as a result of the detachment of Cu atoms fromstep edges caused by the stronger binding of CO relative to that on flat terraces

Britain and West Germany in the 1970's - the economic dimension of the political relationship

SIGLEAvailable from British Library Document Supply Centre- DSC:D88665 / BLDSC - British Library Document Supply CentreGBUnited Kingdo