Structure prototypes rock salt

Among the oxides and sulphides, only CdO adopts the octahedral rock salt structure found with group 2 element, although the solid is normally very deficient in oxygen and the electrons not used in bonding give rise to metallic properties. ZnO and ZnS are prototypes of the tetrahedrally coordinated wurtzite and zinc blende (or sphalerite) structures in fact, ZnS can adopt either structure, as can CdS and CdSe. HgO and HgS have chain structures with linear two-coordination of Hg. 

For metal particles on ionic substrates one can differentiate between interactions with non-polar (stoichiometric) and polar surfaces. The former surfaces are represented by essentially unrelaxed (001) facets of oxides with rock-salt structure, such as MgO(OOl) which is widely utilized as metal support and was addressed in the previous subsection. Oxide supports exhibiting polar surfaces are also common. Clean polar surfaces are unstable and thus difficult to prepare unreconstructed, dehydroxylated, and free of defects [88]. Corundum, a-Al203, is a prototype of such metal oxides. Its most stable Al-terminated (0001) surface... 

The simplest adsorption systems are those in which an inert molecule with a closed-shell electronic configuration is adsorbed on a regular neutral surface of an insulator or a large band gap semiconductor. The prototype for such a situation is the adsorption of CO on the (100) surface plane of aUcah halides or simple cubic metal oxides with rock-salt structure, such as MgO. Indeed, the adsorption of CO on the regular MgO(lOO) surface can be considered as the prototype for physisorption systems. It has been studied extensively both experimentally and theoretically the theoretical treatments comprise cluster approaches as well as periodic calculations, performed both by means of DFT and wave function based methods [70-84]. 

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