Molecular hydrogen potential energy surfaces

Wiesenekker G, Kroes G J and Baerends E J 1996 An analytical six-dimensional potential energy surface for dissociation of molecular hydrogen on Cu(IOO) J. Chem. Phys. 104 7344... 

To understand the fundamental photochemical processes in biologically relevant molecular systems, prototype molecules like phenol or indole - the chromophores of the amino acids tyrosine respective trypthophan - embedded in clusters of ammonia or water molecules are an important object of research. Numerous studies have been performed concerning the dynamics of photoinduced processes in phenol-ammonia or phenol-water clusters (see e. g. [1,2]). As a main result a hydrogen transfer reaction has been clearly indicated in phenol(NH3)n clusters [2], whereas for phenol(H20)n complexes no signature for such a reaction has been found. According to a general theoretical model [3] a similar behavior is expected for the indole molecule surrounded by ammonia or water clusters. As the primary step an internal conversion from the initially excited nn state to a dark 7ta state is predicted which may be followed by the H-transfer process on the 7ia potential energy surface. 

Before a detailed presentation of the ab initio dynamics simulations, first the fundamental difference between atomic and molecular adsorption on the one hand and dissociative adsorption on the other hand has to be addressed. Then I will briefly discuss the question whether quantum or classical methods are appropriate for the simulation of the adsorption dynamics. This section will be followed by a short introduction into the determination of potential energy surfaces from first principles and their continuous representation by some analytical or numerical interpolation schemes. Then the dissociative adsorption and associative desorption of hydrogen at metal and semiconductor surfaces and the molecular trapping of oxygen on platinum will be discussed in some detail. 

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