Clusters quantum properties

Karl-Heinz Meiwas-Broer, Metal Clusters at Surfaces Structure, Quantum Properties, Physical Chemistry, Springer, Berlin, 1999. 

Here, Xni l) denotes the harmonic oscillator wave-functions, (pa(r) and (pb(r) correspond to the states of electrons localized on a and b ions, the index v numbers the hybrid cluster states in the molecular field. It should be noted that, within the scope of the adopted approach, the quantum properties of the vibronic states in a self-consistent field are taken into account. Therefore, it is reasonable to call the proposed approximation quasidynamical. The vibronic states obtained within the scope of the quasidynamical approach are hybrid, i.e. retaining the quantum properties of both electronic and vibrational states. In the case of strong vibronic coupling, i.e. in the case of adiabatic potentials possessing deep minima both the... 

J. M. van Ruitenbeek, Metal clusters on Surface Structure, Quantum properties, Phys. Chem. Series, Springer Verlag, Berlin, 2000. 

Size Dependence of E (Ag, -Ag ). The quantum-size effect on metal clusters redox properties in solution is the most important feature for cluster chemistry in solution. Most of data have been obtained on silver clusters suitable as an experimental model (J-4, 22). 

That the optical properties of such 2D/3D colloid arrays will depend on particle packing densities has been demonstrated by Dusemund et al., who measured the reflectivity of gold colloid films as a function of colloid volume fraction [47]. Although the films were not ordered they showed a clear shift in surface plasmon position with increasing particle volume fraction. The only compromise was that the volume fraction could not be directly determined on the samples from which spectra were taken, but had to be measured on separately prepared TEM grids. Several groups have found that clustered quantum dots exhibit red-shifted fluorescence, a question recently reviewed by Weller [48]. 

Metal clusters are special among nanosized objects. In the bulk phase, metals are conducting, whereas they show semiconducting behaviour for very small particles. Due to quantum-size effects their optical properties are tunable with the system size, and the clusters exhibit properties, which are very much different from those of the bulk phase. 

Meiwes-Broer, K.-H. (2000). Metal clusters at surfaces Structure, quantum properties, physical chemistry (1st ed.). Berlin Springer. 

Much of the work done on metal clusters has been focused on the transition from cluster properties to bulk properties as the clusters become larger, e.g. the transition from quantum chemistry to band theory [127]. 

Clusters are intennediates bridging the properties of the atoms and the bulk. They can be viewed as novel molecules, but different from ordinary molecules, in that they can have various compositions and multiple shapes. Bare clusters are usually quite reactive and unstable against aggregation and have to be studied in vacuum or inert matrices. Interest in clusters comes from a wide range of fields. Clusters are used as models to investigate surface and bulk properties [2]. Since most catalysts are dispersed metal particles [3], isolated clusters provide ideal systems to understand catalytic mechanisms. The versatility of their shapes and compositions make clusters novel molecular systems to extend our concept of chemical bonding, stmcture and dynamics. Stable clusters or passivated clusters can be used as building blocks for new materials or new electronic devices [4] and this aspect has now led to a whole new direction of research into nanoparticles and quantum dots (see chapter C2.17). As the size of electronic devices approaches ever smaller dimensions [5], the new chemical and physical properties of clusters will be relevant to the future of the electronics industry. 

Grossman J C and Mitas L 1995 Quantum Monte Carlo determination of electronic and structural properties of Si clusters (n 20) Phys. Rev. Lett. 74 1323... 

It is thus obvious that among numerous computational methods, first principles quantum chemical approach is indispensable. However, initially first principles quantum chemical calculations required the use of models consisting of a few atoms (clusters) and the range of properties was limited. Since the advent of modem computing resources, as well the models could be extended to cover larger variety of structures as the methodology has been... 

In this brief review we illustrated on selected examples how combinatorial computational chemistry based on first principles quantum theory has made tremendous impact on the development of a variety of new materials including catalysts, semiconductors, ceramics, polymers, functional materials, etc. Since the advent of modem computing resources, first principles calculations were employed to clarify the properties of homogeneous catalysts, bulk solids and surfaces, molecular, cluster or periodic models of active sites. Via dynamic mutual interplay between theory and advanced applications both areas profit and develop towards industrial innovations. Thus combinatorial chemistry and modem technology are inevitably intercoimected in the new era opened by entering 21 century and new millennium. 

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