Time-dependent DFT calculations have been performed on the absorption spectrum of [Fe(CN)6]4- adsorbed a TiO2 anatase nanoparticle model to provide detailed description electronic structure for this prototype system and understand character states involved in molecule --> semiconductor charge transfer process. Our results show that direct injection process from an occupied dye molecular state excited localized few Ti atoms, rather than delocalized conduction state, effectively takes place...

Molecular dynamics simulations of pure silica, sodium silicate, and soda-lime silicate glasses have been carried out using a developed potential that includes polarization effects through the shell model (SM). The has validated available experimental ab initio structural data, such as density, radial angular distributions, coordination environments, network connectivity. In addition, Car-Parrinello molecular glass to obtain reference data for this system. performances SM rigid-ion compared...

The structural properties of three compositions phosphosilicate glasses are investigated by means molecular dynamics computer simulations using a new potential model incorporating polarization effects. Structural features the compared in order to highlight effect composition on different known bioactivities these materials. Changes coordination environment, network connectivity, and ion aggregation with silica content discussed, as they enable us draw microscopic glasses, which supports...

The bioactive mechanism, by which living tissues attach to and integrate with an artificial implant through stable chemical bonds, is at the core of many current medical applications biomaterials, as well novel promising in tissue engineering. Having been employed these for almost 40 years, soda-lime phosphosilicate glasses such 45S5 represent today paradigm materials. Despite their strategical importance field, relationship between structure activity a glass composition biological...

Molecular dynamics simulations of four bioactive silicate glasses containing between 0 (P0) and 12 (P12) mol % P2O5 have been carried out in order to elucidate the structural role phosphorus these materials. In particular, we focused on features which can a direct mechanism dissolution bone bonding. The higher affinity modifier Na Ca cations for coordinating phosphate rather than silicate, together with formation P−O−Si linkages, lead increasing repolymerization network content, principle...

The adsorption of thin water overlayers on the (101) surface TiO2 anatase has been studied through Car-Parrinello molecular dynamics (CPMD) simulations. We compared structural and dynamic properties one two H2O monolayers adsorbed defect-free partially reduced surfaces at 160 K. As for an isolated molecule, we found that dissociation is possible only defective surface. With respect to a single H2O, interaction between molecules reduces barrier: molecule incorporated in monolayer (ML) or...

The adsorption of a water molecule on partially reduced TiO2 anatase (101) surface has been studied by first-principles molecular-dynamics simulations. At variance with the stoichiometric surface, dissociation close to oxygen vacancy is energetically favored compared molecular adsorption. However, no spontaneous was observed in simulation several picoseconds, indicating presence an energy barrier between and dissociated states. free profile along possible path determined through constrained...

The structure and energetics of thin water overlayers on the (101) surface TiO2-anatase have been studied through first-principles molecular dynamics simulations at T = 160 K. At one monolayer coverage, H2O molecules are adsorbed 5-fold Ti sites (Ti5c), forming an ordered crystal-like 2D layer with no significant water−water interactions. For bilayer, both Ti5c bridging oxygen (O2c) form a partially structure, where oxygens occupy regular but orientation is disordered; in addition,...

The hydration of the surface a highly bioactive silicate glass was modeled using ab initio (Car−Parrinello) molecular dynamics (CPMD) simulations, focusing on structural and chemical modifications taking place at glass−water interface immediately after contact way in which they can affect bioactivity these materials. adsorption water dimer trimer dry studied first, followed by extended between liquid water. CPMD trajectories provide atomistic insight into initial stages relevant to...

Fluorinated bioactive glasses (FBGs) combine the antibacterial properties of fluorine with biological activity phosphosilicate glasses. Because their biomedical application depends on release fluorine, detailed characterization environment in FBGs is key to understand properties. Car−Parrinello molecular dynamics (CPMD) simulations have been performed a 45S5 Bioglass composition which 10 mol % CaO has replaced CaF2, and allowed us resolve some longstanding issues about atomic structure...

Recent combined experimental and theoretical studies (Beck et al., Phys. Rev. Lett. 2004, 93, 036104) have provided evidence for Ti=O double-bonded titanyl groups on the reconstructed rutile TiO(2)(011)-(2 x 1) surface. The adsorption of water same surface is now investigated to further probe properties these groups, as well confirm their existence. Ultraviolet photoemission experiments show that adsorbed in molecular form at a sample temperature 110 K. At time, presence 3sigma state spectra...

The adsorption and reactivity of methanol on TiO2 anatase(101) surfaces are studied through first-principles total energy calculations Car−Parrinello molecular dynamics simulations. effects different coverages up to one monolayer surface oxidation states investigated. most stable state involves two states, with specific vibrational electronic properties. Molecular is always favored the stoichiometric surface, even though dissociation becomes increasingly more favorable increasing coverage....

Ab initio (Car-Parrinello) molecular dynamics simulations were carried out to investigate the melt precursor of a modified phosphosilicate glass with bioactive properties, and quench vitreous state. The properties $3000\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ liquid extensively compared those final structure. is characterized by significant fraction structural defects (small rings, undercoordinated overcoordinated ions), often combined together. creation or removal these coordinative in...

The surface of a bioactive (45S) and bioinactive (65S) glass composition has been modeled using shell-model classical molecular dynamics simulations. Direct comparison the two structures allowed us to identify potential role specific features in processes leading integration bioglass implant with host tissues, focusing particular on initial dissolution network. simulations highlight critical network fragmentation sodium enrichment determining rapid hydrolysis release silica fragments...

Car−Parrinello structural optimizations of realistic models the Maya Blue (MB) hybrid material are combined with TDDFT calculations electronic excitation spectra to identify nature fundamental guest−host interactions leading unusual stability this pigment. The comparison features experimental visible spectrum reveals that main mode interaction between host solid (the palygorskite clay) and guest molecule organic indigo dye) involves coordination carbonyl group dye by Al3+ ions exposed at...

The mechanism of sodium migration in low-silica alkali-alkaline earth silicate glasses is investigated through Car-Parrinello molecular dynamics (MD) simulations. transport to the glass surface and its subsequent release critical for use these biomedical applications. analysis MD trajectory, mainly a combination space time correlation functions, reveals complex mechanism, with some common features mixed-alkali several important differences. low site selectivity Na cations this allows them...

Classical and ab initio molecular dynamics (MD) simulations have been carried out to investigate the effect of a different treatment interatomic forces in modeling structural properties multicomponent glasses melts. The simulated system is soda-lime phosphosilicate composition with bioactive properties. Because bioactivity these materials depends on their medium-range features, such as network connectivity Qn distribution (where tetrahedral species bonded n bridging oxygens) silicon...

The incorporation of yttrium in bioactive glasses (BGs) could lead to a new generation radionuclide vectors for cancer therapy, with high biocompatibility, controlled biodegradability and the ability enhance growth healthy tissues after treatment radionuclides. It is essential assess whether what extent affects favourable properties BG matrix: ideally, one would like combine surface reactivity typical BGs slow release radioactive yttrium. Molecular Dynamics simulations show that, compared...

A set of molecular dynamics simulations were performed to investigate the effect cooling rate and system size on medium-range structure melt-derived multicomponent silicate glasses, represented by quaternary 45S5 Bioglass composition. Given significant impact glass degradation applications these materials in biomedicine nuclear waste disposal, bulk structural features which directly affect dissolution process are particular interest. Connectivity matrix, ion clustering nanosegregation,...

We report on the effect of varying Zn2+/Mg2+ ratio structure and biodegradation glasses in an alkali-free system designed glass forming region diopside (CaMgSi2O6)-fluorapatite [Ca5(PO4)3F]-TCP (3CaO·P2O5). The zinc-containing as-mentioned ternary are potential materials for their application bone regeneration tissue engineering. melt-quenched with compositions (mol%), 36.07CaO - (19.24 -x) MgO -xZnO 5.61P2O5- 38.49SiO2- 0.59CaF2, where x varies between 0 10, have been investigated by...

The physiological responses of silicate-based bioactive glasses (BGs) are known to depend critically on both the P content (n(P)) glass and its silicate network connectivity (N(BO)(Si)). However, while bioactivity generally displays a nonmonotonic dependence nP itself, recent work suggest that it is merely net orthophosphate directly links bioactivity. We exploit molecular dynamics (MD) simulations combined with ³¹P ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy explore...