Electronic Origin Charge Entrapment and Polarization

STM imaging and the corresponding c(2 x 2)-20 bond configurations at the Cu(OOl) and the Rh(OOl) surfaces (Part I) indicate that in both cases, adsorbate occupies the fourfold hollow site. Because of the difference in lattice 

However, the forms a bond with an Rh atom immediately underneath and polarizes the remaining four atoms in the surface. The dipoles point to the open end of the surface. The surface dipoles repel one another, and therefore, compressive stress dominates in the Rh(001)-c(2 x 2)-20 surface with a radial outgoing pattern of reconstruction. The Rh(001)-c(2 x 2)-20 scenario holds for the Ni(001)-c(2 x 2)-2C surface as well with compressive stress dominance. Therefore, the same adsorbate induces an opposite stress on the fcc(OOl) surface of Cu and Rh because of the difference in the electronegativity and the lattice size of the host elements. 

20 surface. Therefore, the evolution of the O to the O turns the Cu(OOl) surface stress from tensile to compressive because of charge redistribution and polarization upon adsorbate bond making. 

Likewise, results in tensile, while C leads to compressive stress on the Ni(001) surface. The sp-orbit hybridization of N gives one, and the sp-orbit hybridization gives one non-bonding lone pair to the N- but none to the C-centered tetrahedron, because of their different valences. The N-Ni(001) surface produces the Ni -Ni -Ni -Ni chain, and the C-Ni(OOl) produces the Ni -Ni -Ni -Ni chain along the (11) surface direction. The repulsion between the like charges and the attraction between the unlike ones causes a tensile response of the N-Ni(OOl) surface bonds. The repulsion throughout the rhombus chain leads to the 

Therefore, adsorbate may induce positive or negative smface stress, depending on the substrate geometry and importantly the atomic valence and polarization. These electronic scenarios improve understanding of the adsorbate-induced surface stress and the adsorbate-induced slope change in the temperature dependence of the smface tension of liquid metals. 

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