Density functional theory study of Fe(II) adsorption and oxidation on goethite surfaces

We study the interactions between Fe(II) aqua complexes and surfaces of goethite (alpha-FeOOH) by means of density functional theory calculations including the so-called Hubbard U correction to the exchange-correlation functional. Using a thermodynamic approach, we find that (110) and (021) surfaces in contact with aqueous solutions are almost equally stable, despite the evident needlelike shape of goethite crystals indicating substantially different reactivity of the two faces. We thus suggest that crystal anisotropy may result from different growth rates due to virtually barrierless adsorption of hydrated ions on the (021) but not on the (110) surface. No clear evidence is found for spontaneous electron transfer from an adsorbed Fe(II) hex-aqua complex to a defect-free goethite substrate. Crystal defects are thus inferred to play an important role in assisting such electron transfer processes observed in a recent experimental study. Finally, goethite surfaces are observed to enhance the partial oxidation of adsorbed aqueous Fe(II) upon reaction with molecular oxygen. We propose that this catalytic oxidation effect arises from donation of electronic charge from the bulk oxide to the oxidizing agent through shared hydroxyl ligands anchoring the Fe(II) complexes on the surface

Judicial Governance in Private Law through the Application of Fundamental Rights

Through the acknowledgment and balancing of the conflicting fundamental rights at stake in a private litigation, the courts ‘govern’ societal relationships. This judicial governance complements and adjusts the governance of the concerned societal relationships that takes place at the legislative level. This paper discusses a number of societal governance policies pursued, consciously or inconsciously, by national courts while deciding on private relationships through the application of fundamental rights. Thereby it considers cases decided by courts in Germany, England, France, Italy, the Netherlands, Poland, Portugal, Sweden and Spain. One may observe six major policy trends underlying these decisions: (1) the fight against discrimination, (2) the protection of weaker parties in contract cases, (3) the increasing valorisation of non-economic interests in tort cases, (4) the protection of privacy from intrusions by media, (5) the protection of political rights in privately owned public spaces, and (6) environmental protection in property cases

The newly-adopted Corporate Sustainability Due Diligence Directive: an overview of the lawmaking process and analysis of the final text

This article provides an overview of the process leading up to the adoption of the Corporate Sustainability Due Diligence Directive (CSDDD) and delivers a comprehensive analysis of the Directive’s final text. The article contextualises the design process of the CSDDD within the international normative framework on sustainability due diligence and elaborates on key events surrounding the inter-institutional negotiations between the European Commission, the European Parliament and the Council of the European Union on the Directive. The article then delves into the content of the newly adopted text, highlighting key differences between the final version and the Commission’s original proposal

Modelling the onset of oxide formation on metal surfaces from first principles

The formation of ultrathin oxide layers on metal surfaces is a non-thermally-activated process which takes place spontaneously at very low temperatures within nanoseconds. This paper reports mechanistic details of the initial oxidation of bare metal surfaces, in particular Al(111) and TiN(001), as obtained by means of first-principles molecular dynamics modelling within the Density-Functional Theory. It is shown that the reactions of bare metal surfaces with O2 molecules take place according to a 'hot-atom' dissociative mechanism which is triggered by the filling of the sigma-star antibonding molecular orbital and is characterised by a sudden release of a large amount of kinetic energy. This released energy provides a driving force for metal/oxygen place-exchange processes which are responsible for the onset of oxide formation at virtually 0 K and at oxygen coverages well below 1 monolayer (ML). Further simulations of the oxidation reactions reveal that a disordered ultrathin oxide forms on Al(111), whereas a rather ordered structure develops on TiN(001) following a selective oxidation process which leaves clusters of Ti vacancies in the TiN lattice underneath the oxide layer

Growth of Platinum Clusters in Solution and on Biopolymers: The Microscopic Mechanisms

Thema der vorgelegten Dissertation ist der Mechanismus der Keimbildung und des Wachstums von Platinclustern in Lösung und auf Biopolymeren nach der Reduktion von Platin-Salzen. Die Untersuchung wird auf atomarer Skala durch ab-initio Molekulardynamik mit der Methode von Car und Parrinello durchgeführt. In einem klassischen, generell akzeptierten Mechanismus erfolgt die Aggregation von Pt-Atomen nur nach kompletter Reduktion der Pt(II)-Komplexen zum metallischen Pt(0)-Zustand. Im Gegensatz dazu, in der hier beobachteten Reaktionsablauf entstehen stabile Pt-Pt-Bindungen schon nach einem einzigen Reduktionsschritt. Darüber hinaus wird es gefunden, dass kleine Pt-Cluster durch Addition von unreduzierten PtCl2(H2O)2-Komplexen wachsen können. Das stimmt mit einem experimentell beocbachteten autokatalytischen Clusterwachstumsmechanismus überein. Es wird weiterhin gefunden, dass Pt(II)-Komplexe, die kovalent an DNA oder an Proteine gebunden sind, als sehr effiziente Nukleationszentren für das weitere Metallclusterwachstum wirken können. Das ist eine Konsequenz des starken Donor-Charakters der organischen Liganden, in derer Anwesenheit stärkere Metall-Metall-Bindungen als frei in der Lösung gebildet werden können. In der Tat, in Metallisierungsexperimenten können 5 Nanometer dünne, mehrere Mikrometer lange, regelmässige Clusterkette erzeugt werden, die rein heterogen auf das Biomolekulare Templat gewachsen sind.In this thesis we investigate the molecular mechanisms of platinum cluster nucleation and growth in solution and on biopolymers by means of first-principles molecular dynamics. In contrast with a classical picture where clusters nucleate by aggregation of metallic Pt(0) atoms, we find that Pt--Pt bonds can form between dissolved Pt(II) complexes already after a single reduction step. Furthermore, we observe that small clusters grow by addition of unreduced PtCl2(H2O)2 complexes, consistently with an autocatalytic growth mechanism. Moreover Pt(II) ions covalently bound to biopolymers are found to act as preferred nucleation sites for the formation of clusters. This is a consequence of the strong donor character of the organic ligands which induce the formation of stronger metal-metal bonds than those obtained in solution. In fact, in metallization experiments we obtain a clean and purely heterogeneous metallization of single DNA molecules leading to thin and uniform Pt cluster chains extended over several microns