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Theoretical insights into encapsulated noble metals
Hou, Dianwei ; Heard, Christopher James (advisor) ; Logsdail, Andrew (referee) ; Rubeš, Miroslav (referee)
Noble metals are widely used in industry due to their excellent catalytic and optical properties. Because of limited reserves and high prices, it is desired to make effective use of every atom. It has been possible in recent years to produce subnanometer clusters or even isolated atoms, despite their low resistance against sintering. Furthermore, it has been recently established that the encapsulation of single atoms and subnanometer noble metal clusters can be achieved via trapping at metal oxides, ranging from two-dimensional layered materials to the void space within the pores of zeolites. However, neither the atomistic mechanisms of atom/cluster trapping, nor the means by which they may be optimized are known. Furthermore, the relationship between the physical and electronic state of trapped atoms/clusters and their reactive properties in catalysis are currently only weakly understood. In this thesis, we used theoretical methods ranging from global structure optimization to kinetic Monte Carlo to identify the roles of cluster size, charge state, and the present and type of common adsorbents on the stability, catalytic and optical properties of subnanometre-sized noble metal clusters trapped at metal oxides. This thesis takes the form of three sections: (1) Structure, stability, and migration...
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Computer simulations of characteristics of metal desorption from the Si(111) surface
Sikora, Adam ; Kocán, Pavel (advisor) ; Mysliveček, Josef (referee)
Title: Computer simulations of characteristics of metal desorption from the Si(111) surface Author: Adam Sikora Department: Department of Surface and Plasma Science Supervisor: RNDr. Pavel Kocán, Ph.D. Abstract: In case of desorption of some metals (Pb, In, Ga) from surfaces Si(111) and Ga(111) was by use of integral techniques surprisingly observed zero-order of desorption. Theoretical explanation of zero-order is still missing, since it appears that the conditions that normally lead to desorption of the zeroth order - high diffusivity, the existence of 2D gaseous phase etc. - can not be met. The aim of this work is to develop kinetic Monte Carlo computer code for simulations of atomic processes on the surface of Si(111). The developed code will then be used for investigation of desorption spectra for various parameters and also for finding the parameters which allow the zero-order desorption. Keywords: Kinetic Monte Carlo, temperature programmed desorption, zero-order desorption, Si(111) 1
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