Orbital interactions and chemical reactivity of metal particles and metal surfaces

A review is presented with 101 refs. on chem. bonding to metal surfaces and small metal particles demonstrating the power of symmetry concepts to predict changes in chem. bonding. Ab-initio calcns. of chemisorption to small particles, as well as semiempirical extended Hueckel calcns. applied to the study of the reactivity of metal slabs are reviewed. On small metal particles, classical notions of electron promotion and hybridization are found to apply. The surroundings of a metal atom (ligands in complexes, other metal atoms at surfaces), affect bonding and reactivity through the prehybridization they induce. A factor specific for large particles and surfaces is the required localization of electrons on the atoms involved in the metal surface bond. At the surface, the bond energy is found to relate to the grou8p orbital local d. of states at the Fermi level. The use of this concept is extensively discussed and illustrated for chemisorption of CO and dissocn. of NO on metal surfaces. A discussion is given of the current decompn. schemes of bond energies and related concepts (exchange (Pauli)-repulsion, polarization, charge transfer). The role of non-orthogonality of fragment orbitals and of kinetic and potential energy for Pauli repulsion and (orbital) polarization is analyzed. Numerous examples are discussed to demonstrate the impact of those concepts on chem. bonding theor

A literature study on factors that influence return on investments for e-commerce websites focusing on visibility mechanisms

This study is an investigation of some factors that are believed to have an influence on return on investments of e-commerce websites. The focus is on advertising mechanisms that include search engine marketing and normal web marketing. The literature survey has produced some contradictory statements regarding return-on-investments. Some claims are made of success, while others warn against spending resources on for example banner ads. Further study was done in order to investigate details as to: what are the factors that have major influences on return on investments. As money is invested daily on website visibility activities, a need has also been identified to see these activities deliver on their promises. In this paper, return on investments is defined not only in terms of money, but in terms of awareness. this is because of a strong belief that when a consumer is at a point where they have to make a choice between two brands they are most likely to choose the one that they are more familiar with over the other. these factors include Attitude, Relevancy/congruity, Recall and Complexity