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Shrinking devices to the nanoscale, while still maintaining accurate control on their structure and functionality is one of the major technological challenges of our era. The use of purposely directed self-assembly processes provides a smart alternative to the troublesome manipulation and positioning of nanometer-sized objects piece by piece. Here, we report on a series of recent works where the in-depth study of appropriately chosen model systems addresses the two key points in self-assembly; building blocks selection and control of bonding. We focus in particular on hydrogen bonding because of the stability, precision and yet flexibility of nanostructures based on this interaction. Complementing experimental information with advanced atomistic modeling techniques based on quantum formalisms is a key feature of most investigations. We thus highlight the role of theoretical modeling while we follow the progression in the use of more and more complex molecular building blocks, or "tectons". In particular, we will see that the use of three-dimensional, flexible tectons promises to be a powerful way to achieve highly sophisticated functional nanostructures. However, the increasing complexity of the assembly units used makes it generally more difficult to control the supramolecular organization and predict the assembling mechanisms. This creates a case for developing novel analysis methods and ever more advanced modeling techniques.

Glutathione disulfide (GSSG; -GluCysGly disulfide) was used as a physiologically relevant model molecule to investigate the fundamental adsorption mechanisms of polypeptides onto -alumina nanoparticles. Its adsorption/desorption behavior was studied by enzymatic quantification of the bound GSSG combined with zeta potential measurements of the particles. The adsorption of GSSG to alumina nanoparticles was rapid, was prevented by alkaline pH, was reversed by increasing ionic strength, and followed a nearly ideal Langmuir isotherm with a standard Gibbs adsorption energy of -34.7 kJ/mol. Molecular dynamics simulations suggest that only one of the two glutathionyl moieties contained in GSSG binds stably to the nanoparticle surface. This was confirmed experimentally by the release of GSH from the bound GSSG upon reducing its disulfide bond with dithiothreitol. Our data indicate that electrostatic interactions via the carboxylate groups of one of the two glutathionyl moieties of GSSG are predominantly responsible for the binding of GSSG to the alumina surface. The results and conclusions presented here can provide a base for further experimental and modeling studies on the interactions of biomolecules with ceramic materials.

The catalytic combustion activity of PdPt bimetallic catalysts is governed by oxide phases which form under oxygen-rich operation conditions. We investigate the thermodynamic stability of mixed PdxPt1-xOy phases with the crystal structures of PdO, PtO2, and Pt3O4 within an ab initio thermodynamics framework based on density-functional theory calculations. Our results suggest a complex mixing-demixing behavior of the Pd-Pt-O system upon variations of temperature and oxygen partial pressure. At atmospheric pressure mixed oxides are predicted to be stable only at temperatures below 400-500 K, whereby the presence of Pd 41 ions is stabilized with increasing Pt amount in a PdxPt1-xO2 phase. At intermediate temperatures a mixture of phases becomes stable where PdO coexists with PtO2 or Pt3O4. At high temperatures the oxides decompose directly to form PdPt alloys, except for Pd-rich systems, where PdO and metallic Pt coexist within a small temperature window.

The formation of a hydroxylated native oxide layer on Si(001) under wet conditions is studied by means of first principles molecular dynamics simulations. Water molecules are found to adsorb and dissociate on the oxidized surface leading to rupture of Si-O bonds and producing reactive sites for attack by dissolved dioxygen or hydrogen peroxide molecules. Tensile strain is found to enhance the driving force for the dissociative adsorption of water, suggesting that similar reactions could be responsible for environmentally driven subcritical crack propagation in silicon.

We have studied the segregation of P and B impurities during oxidation of the Si(100) surface by means of combined static and dynamical first-principles simulations based on density functional theory. In the bare surface, dopants segregate to chemically stable surface sites or to locally compressed subsurface sites. Surface oxidation is accompanied by development of tensile surface stress up to 2.9 Nm(-1) at a coverage of 1.5 monolayers of oxygen and by formation of oxidised Si species with charges increasing approximately linearly with the number of neighbouring oxygen atoms. Substitutional P and B defects are energetically unstable within the native oxide layer, and are preferentially located at or beneath the Si/SiOx interface. Consistently, first-principles molecular dynamics simulations of native oxide formation on doped surfaces reveal that dopants avoid the formation of P-O and B-O bonds, suggesting a surface oxidation mechanism whereby impurities remain trapped at the Si/SiOx interface. This seems to preclude a direct influence of impurities on the surface electrostatics and, hence, on the interactions with an external environment.

For over a century, platinum oxides find technologically relevant applications in various fields ranging from catalysis to electrochemistry and nanoelectronics. We have performed a density functional theory study of the PtO, Pt3O4, and PtO2 bulk oxide phases. In our calculations, PtO and Pt3O4 present metallic character at the simple generalized gradient approximation level. The application of Hubbard corrections to the Kohn-Sham Hamiltonian opens a small gap in the electronic band structure of PtO, but not of Pt3O4, in which metallic Pt-Pt bonds are revealed by a Bader analysis of the calculated electronic structure. These results, together with the noninteger oxidation number of the Pt ions, are indicative of metallicity of the Pt3O4 phase which may be consistent with the known metallic character of platinum bronzes. Moreover, we have calculated the relative thermodynamic stabilities of platinum oxide Wulff's particles and discussed the results in the context of catalysis. Finally, we have predicted that the formation of alpha-PtO2 nanotubes could be energetically feasible. This result is of potential interest both for nanotechnological and catalytic applications and may explain the formation of curled alpha-PtO2 sheets observed in high-resolution transmission electron microscopy images.

FGM composites have been prepared using Al2O3 and NiAl powders. Pure Al2O3 and NiAl layers have been joined trough a mixed layer (70% vol Al2O3 and 30% vol NiAl). The residual stress in Al2O3 has been experimentally determined by monitoring the stress-induced frequency shift of a fluorescence band due to chromium impurities naturally present in the Al2O3 powder. The stress in Al2O3 is compressive increasing in absolute value when moving from pure alumina to pure NiAl. In the mixed Al2O3/NiAl the stress present large fluctuations from site to site due to local microstructural inhomogeneities.

The introduction of computer simulations has promoted significant design optimisation and cost reduction in many fields of engineering. Nowadays, atomistic modelling of materials is becoming time and cost effective not only for pure research, but also for cutting-edge engineering applications. In this paper we present an overview of atomistic materials modelling, with particular emphasis on Quantum Mechanical (QM) simulations based on the Density Functional Theory (DFT). As examples of applications to ceramics, we report about computational investigations of the oxidation of metal surfaces, of the chemical reactivity of biomaterials, of the reinforcement mechanisms in nano-composites, and of graphitisation of SiC.

Herein we report on the direct observation of chiral recognition events of adsorbed diphenylalanine by scanning tunneling microscopy (STM). The interaction among individual di-d-phenylalanine (d-Phe-d- Phe) molecules and the discrimination of d-Phe-d-Phe from its enantiomer l-Phe-l-Phe on Cu(110) is followed by STM and rationalized by using first principles and classical molecular dynamics techniques. We find that the stereoselective assembly of adsorbed di-phenylalanine enantiomers into molecule pairs and chains takes place through mutually induced conformational changes, thereby illustrating at the single-molecule level the more than half a century old prediction of Pauling.

Domain formation and polarization in ferroelectric films probably are strongly influenced by intrinsic stress. Raman microscopy offers the possibility to get informations about the stress state even in film structures with lateral dimensions of several ten microns. PZT (Pb[Zr,Ti]O 3 ) microstructures with Pt bottom electrodes sputtered on silicon wafers were investigated using the Raman peak of the single crystalline silicon. Near edges of Pt and PZT films Raman shifts |Δv| ≤ 1,5 cm -1 were measured corresponding to stresses in the silicon substrate near the interface in the order of several hundred MPa. The Raman shift profiles are dependent on the particular geometry of the investigated structures and specific microstructure defects near the edge. An estimate of the stress in the PZT film was obtained by modelling the stress in the silicon as a function of the distance from one edge using a finite element code.

We investigate the dynamical features of the adsorption of diphenylalanine molecules on the Cu(I 10) surface and of their assembling into supramolecular structures by a combination of quantum and classical atomistic modeling with dynamic scanning tunneling microscopy and spectroscopic experiments. Our results reveal a self-assembling mechanism in which isolated adsorbed molecules change their conformation and adsorption mode as a consequence of their mutual interactions. In particular, the formation of zwitterions after proton transfer between initially neutral molecules is found to be the key event of the assembling process, which stabilizes the supramolecular structures. Because of the constraints on the intermolecular bonds exerted by the surface-molecule interactions, the assembly process is strictly stereoselective, And may suggest a general model for patterning and functionalization of bare metal surfaces with short chiral peptides.