Heterogeneous catalyzed processes are highly significant to the chemical industry. Dissociative chemisorption (DC) of molecules on surfaces is always considered as a step with a high degree of rate... Show moreHeterogeneous catalyzed processes are highly significant to the chemical industry. Dissociative chemisorption (DC) of molecules on surfaces is always considered as a step with a high degree of rate control for heterogeneous catalysis. Our ability to comprehend the different mechanisms underlying DC on metal surfaces could benefit significantly from the availability of an accurate database for the barrier heights of elementary molecule-metal surface reactions. In this work, we used a recent implementation of specific reaction parameter (SRP) to density-functional theory (DFT) (SRP-DFT) to develop potential energy surfaces (PESs) for molecule-surface reactions. The PESs were used for molecular beam simulations and compared with molecular beam experiments. The barrier heights extracted from these PESs are now used for benchmarking. Show less
Metals surfaces form a group of effective catalysts for the reaction of small molecules such as hydrogen (H2). In order to improve the predictive power of theory with respect to the catalytic... Show moreMetals surfaces form a group of effective catalysts for the reaction of small molecules such as hydrogen (H2). In order to improve the predictive power of theory with respect to the catalytic activity of small molecules reacting at metal surfaces, the way in which metal surfaces modify the potential energy of molecules needs to be understood at a fundamental level. Currently density functional theory (DFT) is the only electronic structure method that is accurate enough to achieve chemical accuracy while being cheap enough to make large comparative studies feasible. The work in this thesis is concerned with the creation of highly accurate density functionals that can give a simultaneously good description of the metal surface, the molecule, and the molecule interacting with the metal surface, as well as the description and simulation of supersonic molecular beam experiments and associative desorption experiments needed to validate the obtained results. Show less
This research was about to better understanding of heterogeneous catalyzed processes which would help to design better and more efficient catalysts but it is hard to achieve because of their high... Show moreThis research was about to better understanding of heterogeneous catalyzed processes which would help to design better and more efficient catalysts but it is hard to achieve because of their high level of complexity. In this way, we compared molecular beam experiments with molecular dynamics simulations to improve over the theoretical method used, called density functional theory (DFT), to achieve chemical accuracy (i.e., errors smaller than 1 kcal/mol) for the reaction studied. Show less
Nour Ghassemi, E.; Wijzenbroek, M.; Somers, M.F.; Kroes, G.J. 2017
Using semi-empirical density functional theory and the quasi-classical trajectory (QCT) method, a specific reaction parameter (SRP) density functional is developed for the dissociation of... Show moreUsing semi-empirical density functional theory and the quasi-classical trajectory (QCT) method, a specific reaction parameter (SRP) density functional is developed for the dissociation of dihydrogen on Pt(1 1 1). The validity of the QCT method was established by showing that QCT calculations on reaction of D2 with Pt(1 1 1) closely reproduce quantum dynamics results for reaction of D2 in its rovibrational ground state. With the SRP functional, QCT calculations reproduce experimental data on D2 sticking to Pt(1 1 1) at normal and off-normal incidence with chemical accuracy. The dissociation of dihydrogen on Pt(1 1 1) is non-activated, exhibiting a minimum barrier height of −8 meV. Show less
What is the catalytic role played by titanium in the hydrogen storage material NaAlH4? This thesis aims at unraveling the dynamics of an elementary reaction: H2 dissociation on Ti/Al(100) surfaces.... Show moreWhat is the catalytic role played by titanium in the hydrogen storage material NaAlH4? This thesis aims at unraveling the dynamics of an elementary reaction: H2 dissociation on Ti/Al(100) surfaces. Although this reaction is not the rate limiting step in the hydrogen storage of NaAlH4, it is an important reaction to produce atomic hydrogen for the other reaction steps. To achieve the stated goal, we test a large set of possible slab models to represent the Ti/Al(100) surface. After considering the stability of the slab model itself and the barrier height for H2 dissociation, we carefully select two possible slab models: (1) the 1/2 ML Ti-covered c(2 _ 2)-Ti/Al(100) surface with Ti atoms in the second layer, (2) the 1 ML Ti-covered c(2 _ 2)-Ti/Al(100) surface with Ti atoms in the first and third layers. Using these two slab models, potential energy surfaces (PES) are calculated. The H2 dissociation probabilities and rate constants are then calculated. The results suggest that the 1 ML Ti-covered c(2 _ 2)-Ti/Al(100) surface may be the most realistic model for H2 dissociation on Ti/Al(100) surfaces relevant for the hydrogen storage material NaAlH4. In this thesis, time-dependent wave packet, quasi-classical and classical dynamics, and transition state theory have been imployed to calculate the micro-canonical reaction probabilities and canonical reaction rate constants. Show less
