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Hydrogen atoms at the palladium surface, at the MgO surface and at the Pd-MgO metal-support boundary. Towards computer modelling of the spillover effect

Bartczak W.M., Stawowska J.

Materials Science Poland

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2006

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Vol. 24, No. 2/1

421--432

EN

The work is devoted to computer modelling of interactions of atomic hydrogen with palladium and MgO surfaces, and with Pd atoms adsorbed on MgO surface. Quantum calculations were performed using the methods of the Density Functional Theory (DFT) with gradient-corrected functionals for electron exchange and correlation. The potential energy surfaces were calculated for a hydrogen atom interacting with Pd and MgO surfaces. The results indicate an easy (0.17 eV activation barrier) diffusion of hydrogen atoms over the metal surface. A possibility of migration of H atoms from the metal surface onto the MgO support surface (the "spillover effect") is discussed. It was found that the transfer of a hydrogen atom from the vicinity of a Pd atom to O sites of the MgO surface results in the energy gain of the order of 0.5 eV. The transfer, however, is an activated process with the activation energy about 0.8 eV.

2

Proces reformingu metalu ditlenkiem węgla : możliwości badawcze metod symulacji komputerowej

Bartczak W. M., Stawowska J.

Przemysł Chemiczny

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2003

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T. 82, nr 3

193-198

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Oddziaływanie wodoru z powierzchnią katalizatorów bimetalicznych

Bartczak W. M., Stawowska J., Romanowski S.

Przemysł Chemiczny

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2003

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T. 82, nr 8-9

664-670

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Modelowanie komputerowe procesu dezaktywacji katalizatora metalicznego przez depozyt węglowy

Stawowska J., Bartczak W. M.

Przemysł Chemiczny

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2003

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T. 82, nr 8-9

778-782

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Modelowanie oddziaływania wodoru z metalami przejściowymi za pomocą teorii funkcjonałów gęstości (DFT). Perspektywa kwantowych modeli katalizy heterogenicznej

Bartczak W.M., Romanowski S., Łandwijt M.

Wiadomości Chemiczne

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2001

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[Z] 55, 7-8

629-655

EN

Computer modelling of catalytic effects of a series of the transition metals and their alloys on the process of dissociation of molecular hydrogen has been performed. The project was composed of three stages. First, the binding energy versus the internuclear distance has been calculated for a series of metal dimers and mixed dimers: Ni2, NiCu, Cu2, Ag2, AgPd, Pd2 Au2, Pt2, AuPt. It has been shown that the traditional methods of quantum chemistry: the ZINDO semiempirical methods and the Hartree-Fock methods do not work properly in the case of the transition metal dimers. In contrast with these methods, the calculations based on the nonlocal version of the density functional theory (DFT) provide very good results, in full agreement with available experimental data concerning the dissociation energies and equilibrium bond lengths of the metal dimers. Then, using the fitted Morse form of the potential interaction between the metal atoms, the Molecular Dynamics (MD) simulations have been performed in order to obtain the atomic structures appearing in the alloys. The third part of the project includes the quantum-chemical calculations of hydrogen atom and hydrogen molecule positioned over the metallic dimers. The interatomic distances of the dimers were taken from the MD calculations. A range of the distances of hydrogen from the metal dimers was scanned. The evolution of energy and electron density with the hydrogen distance from certain dimers, like NiCu, AgPd and Pd2, clearly exhibits the process of the hydrogen molecule dissociation. On a basis of these calculations a measure of catalytic power of the metals was defined and the series of metals and alloys was ordered according to their catalytic power. It was found that the highest catalytic power with respect to the hydrogen dissociation process is exhibited by NiCu alloys. All the quantum-chemical calculations have been performed using the methods of the Density Functional Theory. The nonlocal version of the DFT was applied with the gradient-corrected hybrid functionals for electron exchange and correlation. The GAUSSIAN 98 suite of programs was employed in the calculations.

6

Rozwój metod eksperymentu komputerowego i ich zastosowanie w badaniach procesów fizykochemicznych inicjowanych radiacyjnie

Bartczak W. M.

Postępy Techniki Jądrowej

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1999

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vol. 42, z. 3

32-44

PL

W artykule autor przedstawił przegląd tematyki badawczej z zakresu metod eksperymentu komputerowego w zastosowaniu w badaniach procesów fizykochemicznych inicjowanych radiacyjnie.

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Density functional study of hydrogen adsorption on selected transition metals and their alloys

Romanowski S., Pietrzak T., Bartczak W. M.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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Vol. 47, No. 2

143-151

EN

The present note shows preliminary results of the non-local density functional calculations of energy of the hydrogen adsorption on the alloys NixCU(1)-x, AgxPd(1)-x, AuxPt(1)-x, where 0 < x < 1. The aim of the calculations was to provide an integrated measure of the catalytic power of a given alloy for the H2 dissociation reaction. It was found that the highest value of the catalytic power is exhibited by Nix CU1-x alloys with x between 0.3 and 0.6 and some AUxPtl-x alloys and the neat metals Ni and Pt.

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Electron localization in liquid methanol. Quantum Path-Integral simulation

Bartczak W.M., Sopek M.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 7S

1798-1825

EN

An excess electron o liquid methanol at room temperature was studied using the method of Path-Integral Molecular Dynamics simulation. A compact charge distribution of an excess electron, suggesting a localized electron state, was found. The charge distribution is centred in a cavity built of methanol according to the traditional picture of the solvated electron. Various radial distribution functions were calculated reflecting the correlations between the cavity centre or the electron charge density and the sites of the methanol molecule. The correlations are stronger than in the case of the hydrated electron. Interpretation of the radial distribution functions as well as the bond-angle distribution functions leads to a picture of 4 methanol molecules forming the solvation shell of the solvated electron. The molecules are oriented towards the centre of the electron density by the OH bonds. The coordination number of the solvated electron agree with the conclusions from electron magnetic resonance experiments.

9

Molecular dynamics calculations for a series of transition metals and their alloys

Romanowski S., Pietrzak T., Bartczak W. M.

Bulletin of the Polish Academy of Sciences. Chemistry

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1998

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Vol. 46, No. 4

397-410

EN

The present note shows preliminary results of the Molecular Dynamics sim/ tions (NPT ensemble at room temperature) of the neat metals Ni, Cu, Ag, Pd, Au, Pt and the alloys NixCul-x, AgxPtl-x, AuxPd(l), where 0