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The thermodynamic stability of hydroxylated graphane, that is, fully sp3 graphene derivatives coordinated with -H and -OH groups, has been recently demonstrated by ab initio calculations. Within the density functional theory approach, we investigate the electronic property modifications of graphane by progressive hydroxylation, that is, by progressively substituting -H with -OH groups. When 50% of graphane is hydroxylated, the energy bandgap reaches its largest value of 6.68 eV. The electronic affinity of 0.8 eV for graphane can widely change in the 0.28-1.60 eV range depending on the geometric configuration. Hydroxylated graphane has two interfaces with vacuum, hence its electron affinity can be different on each interface with the formation of an intrinsic dipole perpendicular to the monolayer. We envisage the possibility of using hydroxylated graphane allotropes with tunable electronic affinity to serve as interfacial layers in 2D material-based heterojunctions.

The solubilization mechanism of lipid membranes in the presence of Triton X-100 (TX-100) is investigated at molecular resolution using molecular dynamics (MD) simulations. Thanks to the large time and length scales accessible by the hybrid particle-field formulation of the models employed here, the complex process of membrane solubilization has been studied, with the goal of verifying the three stage model reported in the literature. DPPC lipid bilayers and vesicles have been studied at different concentrations of the TX-100 detergent employing coarse grained (CG) models. Systems up to ∼600.000 beads, corresponding to more than 2 millions heavy atoms, have been simulated. Moreover, in order to clarify several experimental pieces of evidence, both slow and fast detergent partition scenarios have been investigated. Flat and curved (vesicles) lipid bilayer surfaces, interacting with TX-100, have been considered to study the curvature effects on the detergent partition rate in the membrane. Shape and conformational changes of mixed DPPC/TX-100 vesicles, as a function of TX-100 content, have also been studied. In particular, high curvature surfaces, corresponding to a higher local TX-100 content, promote a membrane rupture. In flat lipid surfaces, on the time scale simulated the detergent partition is almost absent, following a different pathway of the solubilization membrane mechanism. © 2017 the Owner Societies.

Corrosion property of iron in high temperature stagnant liquid lead has been studied using molecular dynamics method. The method was used to predict the limit values of the injected oxygen into the liquid lead for maximum corrosion inhibition of iron. It is from experimental results, in order to inhibit the corrosion at possible lowest rate then a stable self-healing protective iron oxide layer should be developed at the surface of steel continuously. In this research we investigated the iron corrosion and it can be predicted that the protective oxide layer may be formed by injecting oxygen within the range of 5.35 × 10-2 wt% to 8.95 × 10-2 wt% (for observed temperature 750 C). The oxygen 5.35 × 10-2 wt% is the lower limit to prevent high dissolution of iron while the oxygen content of 8.95 × 10-2 wt% is the upper limit to avoid high precipitation of lead oxide. We also guess that effect of oxygen injection into liquid lead creates a thin oxygen barrier that separating the liquid lead and iron oxides from direct interaction. The iron oxides layer and oxygen barrier then may be regarded as double corrosion inhibition. © 2013 Elsevier Ltd. All rights reserved.

Doping of MgH2 with transition metals and their oxides is well-known procedure to improve its hydrogen (de) sorption properties, namely to lower the temperature of desorption and to achieve the kinetics speedup. In order to assess the influence Ti and TiO2 doping has on H mobility and to characterize structurally and electronically observed differences, MgH2-Mg interface doped with both Ti and TiO2 have been studied using ab-initio interface molecular dynamics and bulk calculations. Results suggest different mechanisms of MgH2 structure destabilization. The presence of dopants significantly stabilize MgH2-Mg interface, which is confirmed by work of adhesion computation. Calculated formation energies show that interface system with doped TiO2 is more stable. In terms of H mobility, molecular dynamics simulations confirm that Ti doping is more effective than TiO2 in lowering the desorption temperature. The mobility of hydrogen atoms close to dopant is much higher in the case of Ti than in the case of TiO2. Electronic structure characterization reveals that oxygen atoms with high electron affinity forms more pronounced ionic bonding with Ti and the other neighbor Mg atoms. This in turn cause a shorter Ti-H bonds in first coordination than in the case of Ti doping and further reduction of H atoms mobility. This is in accordance with molecular dynamics predictions. (C) 2016 Elsevier B.V. All rights reserved.

The interface of biological molecules with inorganic surfaces has been the subject of several recent studies. Experimentally some amino acids are evidenced to play a critical role in the adhesion and selectivity on oxide surfaces; however, detailed information on how the water molecules on the hydrated surface are able to mediate the adsorption is still missing. Accurate total energy ab initio calculations based on dispersion-corrected density functional theory have been performed to investigate the adsorption of selected amino acids on the hydrated ZnO(101¯0) surface, and the results are presented and discussed in this paper. We have also investigated the role played by water in the determination of the most energetically favorable adsorption configurations of the selected amino acids. We have found that for some amino acids the most energetically favorable configurations involve the deprotonation of the molecule if the water screening is not effective. © 2015 American Chemical Society.

The corrosion of structural materials used in fast nuclear reactor design is a current major problem. It is due to the use of liquid metal as a coolant candidate in the heat transfer system. The liquid metal as lead-bismuth eutectic was found to make high corrosion to structural material as steel. One of the solutions of this problem is to inject some inhibitor into liquid metal. In this current work we simulate the effect of nitrogen injection as inhibitor candidate. The simulation will predict the proper concentration of injected nitrogen and also observe the microscopic structure of the material before and after injection to know the ability of nitrogen as an inhibitor. The simulation follows the molecular dynamics method and for preliminary study we use iron material rather than steel. We also use lennard-jones potential for simplification of the study. It is from our simulation we see nitrogen shows better corrosion mitigation compare with oxygen as in our previous study. The effective inhibition can be achieved by injecting at least 0.056wt.% nitrogen. This amount seems to be able to reduce the corrosion level of iron till about 99.5% for high corrosion at temperature 750 °C. © Published under licence by IOP Publishing Ltd.

A multiscale scheme is proposed and validated for Triton X-100 (TX-100), which is a detergent widely employed in biology. The hybrid particle field formulation of the model allows simulations of large-scale systems. The coarse-grained (CG) model, accurately validated in a wide range of concentrations, shows a critical micelle concentration, shape transition in isotropic micellar phase, and appearance of hexagonal ordered phase in the experimental ranges reported in the literature. The fine resolution of the proposed CG model allows one to obtain, by a suitable reverse mapping procedure, atomistic models of micellar assemblies and of the hexagonal phase. In particular, atomistic models of the micelles give structures in good agreement with experimental pair distance distribution functions and hydrodynamic measurements. The picture emerging by detailed analysis of simulated systems is quite complex. Polydisperse mixtures of spherical-, oblate-, and prolate-shaped aggregates have been found. The shape and the micelle behavior are mainly dictated by the aggregation number (Nagg). Micelles with low Nagg values (∼40) are spherical, while those with high Nagg values (∼140 or larger) are characterized by prolate ellipsoidal shapes. For intermediate Nagg values (∼70), fluxional micelles alternating between oblate and prolate shapes are found. The proposed model opens the way to investigations of several mechanisms involving TX-100 assembly in protein and membrane biophysics. © 2015 American Chemical Society.

Magnesium hydride is a very promising material for solid-state hydrogen storage. However, some drawbacks have to be overcome to use it in real applications. The use of catalysts is a viable solution to lower the desorption temperature and increase the overall kinetics. An accurate model has been developed to study the mechanism of action of the catalyst and how it interacts with the interface MgH2-Mg, through which H atoms diffuse. The accurate evaluation of the work of adhesion and defect energy formation, versus the distance from the interface are linked to the atomic-scale structural distortion induced by the catalyst. Moreover, molecular dynamics simulations at several temperature provide a clear description of the desorption mechanism and an estimate of the desorption temperature. © 2015 Hydrogen Energy Publications, LLC.

After a brief review of the basic properties of TiSi 2 phases recently obtained by molecular dynamics simulations, we show the self-diffusing species at high temperatures in both the C54 and C49 structures to be silicon, by hopping through a first neighbours network. The kinetic parameters and the diffusion paths for Si diffusion by vacancies and interstitials are reported, pointing out that diffusion in the C49 structure by SiI vacancies is strongly favoured, due to the very low formation energy they display.

Corrosion of structural materials in high temperature molten lead-bismuth eutectic is a major problem for design of PbBi cooled reactor. One technique to inhibit corrosion process is to inject oxygen into coolant. In this paper we study and focus on a way of inhibiting the corrosion of iron using molecular dynamics method. For the simulation results we concluded that effective corrosion inhibition of iron may be achieved by injection 0.0532 wt% to 0.1156 wt% oxygen into liquid lead-bismuth. At this oxygen concentration the structure of iron material will be maintained at about 70% in bcc crystal structure during interaction with liquid metal. © 2014 AIP Publishing LLC.

Hydrogen desorption from hydride matrix is still an open field of research. Extensive, density functional theory based, ab-initio molecular dynamics simulations of MgH2-Mg interface catches the atomic level structural mechanism leading to hydrogen desorption. The numerical model estimates the desorption temperature for an interface with Fe catalyst in excellent agreement with experimental results. Formation energies and the analysis of the structural data reveal the role played by the catalysts to lower the desorption temperature. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

In this work total and partial density of states were calculated for small single wurtzite CdS nanoparticle, quantum dots, with diameter below 2 nm, performing DFT pseudopotentials calculations with generalized gradient approximation. The cluster was previously heated at different temperatures ranging from 100 to 600 K-, by means of Car-Parrinello ab-initio molecular dynamics, finding a stable phase after 340 K. Another stable phase is reached at higher temperature, more than 480 K, where surface migrations play an important role in the determination of final atomic configuration. Density of states was obtained for the structures heated at 100 K, 280 K 330 K, 340 K, 480 K and 570 K and substantial modifications were found after 340 K where the superficial effects cause some alterations of the intermediate electronic states around the band gap. From the partial density of states it has been clearly showed that the atoms on the surface have a main role on the formation of the intermediate states on the band gap. This effect is meaningful for small particles where the fraction of the surface atoms is greater than the fraction of the core atoms.Copyright © 2013 American Scientific Publishers.

The upper threshold of hydrogen adsorption in Li-doped and hydrogenated carbon nanotube densely packed arrays is calculated to check the ability of such systems to fulfill the target indicated by the United States Department of Energy (DOE). To this aim, model potential parameters have been obtained by Density Functional Theory and have been used to calculate the adsorption isotherms in honeycomb arrays containing up to seven tubes by means of Grand-Canonical Monte Carlo simulations. A hybrid model has been developed involving both atomistic potentials for short-range interactions and integrated potentials for hydrogen interacting with distant tubes. In the pressure range explored, it is shown that the hydrogen adsorption performances of Li-doped carbon nanotubes arranged in close packed honeycomb arrays, while being enhanced with respect to pristine carbon nanotubes, are still well below the DOE targets. © Springer Science+Business Media 2013.

We analyze from a computational viewpoint the conformational and dynamical properties of the interesting oligopeptide that is reported to bind specifically to titania surfaces. First-principles simulations based on Density Functional Theory (DFT) and classical Molecular Dynamics (MD) are carried out to investigate both the structure and the stability of single amino acids and of the full peptide on the (101) surface of TiO2 in the anatase crystalline structure. Moreover the strength of the adhesion is estimated by pulling the peptide away from the surface. Our results shed light on the role played by some amino acids that are known to be essential in selective adsorption on TiO2, as well as on the peptide structural conformation upon the surface.Copyright © 2013 American Scientific Publishers.

The long-term objective of the European Fusion Development Agreement (EFDA) fusion materials programme is to develop structural and armor materials in combination with the necessary production and fabrication technologies for reactor concepts beyond the International Thermonuclear Experimental Reactor. The programmatic roadmap is structured into four engineering research lines which comprise fabrication process development, structural material development, armor material optimization, and irradiation performance testing, which are complemented by a fundamental research programme on "Materials Science and Modeling." This paper presents the current research status of the EFDA experimental and testing investigations, and gives a detailed overview of the latest results on materials research, fabrication, joining, high heat flux testing, plasticity studies, modeling, and validation experiments. (C) 2013 Elsevier B.V. All rights reserved.

In this letter, the strain field below uncapped Ge islands of a different shape on a Si(001) substrate is estimated by molecular dynamics simulations at a realistic scale. Comparison to the Fourier transform maps of transmission electron micrographs, recently reported in literature, shows a very good agreement. We point out that the complex deformation in silicon, just below the edges of the Ge islands, is far from being uniaxial. The stress distribution generated by such a strain determines the range of interdot repulsion. (C) 2002 American Institute of Physics.

Tight binding molecular dynamics is used to predict the structure and the total energy of the most relevant intrinsic point defects in C54 and C49 TiSi2. The comparison between the relative formation energies of point defects of the two phases in contact with a Si substrate suggests that the metastable C49 form has a higher concentration of point defects. In particular, we point out that Si vacancies and (010) stacking faults should be quite common in the C49 structure. This issue could be important in explaining the kinetic advantage of the latter phase in film growth by solid state reaction.

Molecular dynamics simulations by a tight binding potential provide new interesting information on the ground state properties of the TiSi2 phases. In particular, we have compared some structural, elastic, thermodynamic and electronic properties of the C49, the C54 and the amorphous phases. It turns out that the C49 structure is much softer than the C54, also displaying a melting temperature some 300-400 K below the one for the C54, in agreement to very recent experimental results. The amorphous phase is energetically and structurally more akin to the C49 than to the C54 phase. On the basis of these results we suggest the higher formation kinetics of the former to be related to an intrinsic advantage in the growth stage. (C) 2000 Elsevier Science B.V. All rights reserved.

The current magnetic confinement nuclear fusion power reactor concepts going beyond ITER are based on assumptions about the availability of materials with extreme mechanical, heat, and neutron load capacity. In Europe, the development of such structural and armour materials together with the necessary production, machining, and fabrication technologies is pursued within the EFDA long-term fusion materials programme. This paper reviews the progress of work within the programme in the area of tungsten and tungsten alloys. Results, conclusions, and future projections are summarized for each of the programme's main subtopics, which are: (1) fabrication, (2) structural W materials, (3) W armour materials, and (4) materials science and modelling. It gives a detailed overview of the latest results on materials research, fabrication processes, joining options, high heat flux testing, plasticity studies, modelling, and validation experiments. (C) 2012 Elsevier B.V. All rights reserved.