Interaction Of Atomic Oxygen Research Articles

Unraveling the interaction between singlet state atomic oxygen O(1D) and water: toward the formation of oxywater and hydrogen peroxide.

We performed high-level quantum mechanical calculations to explore the interaction of atomic oxygen in the ground triplet state, O(3P), and the excited singlet state, O(1D), with water. We reported the potential energy curves for a few lowest electronic states when an atomic oxygen approaches the oxygen of a water molecule. Our results predict the formation of a singlet oxywater species as the product of O(1D) and H2O which lies about 149.33 kJ mol-1 below the total energy of a singlet oxygen atom and a water molecule. Our calculations predict that an O(3P) atom interacting with a water molecule forms a triplet oxywater complex with a shallow minimum on the triplet potential energy surfaces. We examined the transition of the singlet state oxywater species to hydrogen peroxide through the unimolecular reaction pathway, a (1,2)-hydrogen shift. We reported the structural properties, vibrational frequencies, and dipole moments of oxywater species, the transition state, and hydrogen peroxide. We also reported the energy barrier for the transition, and we provided an estimate for the respective reaction rate constant. In addition, we investigated the impact of solvents on the reaction pathway using an implicit solvation model of water. We predict that a singlet state oxywater species has a longer lifetime in a water environment than in the gas phase.

Study on the Effects and Mechanism of Temperature and AO Flux Density in the AO Interaction with Upilex-S Using the ReaxFF Method

Atomic oxygen (AO), which is one of the most predominant and conspicuous space environmental factors in the low earth orbit, leads to severe deterioration of polymeric materials in spacecraft. The AO flux density and ambient temperature vary while a craft orbits in space; thus, it is necessary to pay close attention to the flux density and temperature effects on the mechanism of the AO interaction with materials. In past years, polyimide has been widely used on spacecraft due to its excellent performance—that is the reason why we chose Upilex-S as the object for study. It was analyzed using the ReaxFF reactive force field molecular dynamics simulation, respectively from the aspect of impact-induced temperature variation, mass loss, reaction product and erosion yield. The results show that dense AO deposition on the surface impedes further erosion at low temperatures, and the AO interaction with Upilex-S is exacerbated as the ambient temperature increases. However, the accelerating rate is inversely proportional to the ambient temperature, which means the higher the ambient temperature is, the slower it increases. On the other hand, the interaction rate of AO induced to Upilex-S is aggravated as the flux density increases at the lower stage, while the interaction rate begins to drop as the flux density increases at the higher level. The AO erosion effect is a complicated process rather than a simple summation of single atomic oxygen interactions. Our study could be used as a technical reference for the wide usage of Upilex-S on spacecraft.

Interaction of Atomic Oxygen with a Polycrystalline Au Surface: XPS and TPD Study

Interaction of Atomic Oxygen with a Polycrystalline Au Surface: XPS and TPD Study

Informing air-carbon ablation modeling with theoretical calculations of atomic oxygen and nitrogen interacting with carbon surfaces.

To understand the gas-surface chemistry above the thermal protection system of a hypersonic vehicle, it is necessary to map out the kinetics of key elementary reaction steps. In this work, extensive periodic density functional theory (DFT) calculations are performed to elucidate the interaction of atomic oxygen and nitrogen with both the basal plane and edge sites of highly oriented pyrolytic graphite (HOPG). Reaction energies and barriers are determined for adsorption, desorption, diffusion, recombination, and several reactions. These DFT results are compared with the most recent finite-rate model for air-carbon ablation. Our DFT results corroborated some of the parameters used in the model but suggest that further refinement may be necessary for others. The calculations reported here will help to establish a predictive kinetic model for the complex reaction network present under hypersonic flight conditions.

Small palladium clusters and their adducts with atomic oxygen

A systematic investigation on small Pdn clusters (n = 1 ÷ 8) and their interaction with atomic oxygen was conducted at DFT level. A model to describe cohesive energy for small sized clusters based on a topological approach was proposed and validated. On the basis of the bond length, the stabilisation electronic energy and the second electronic energy difference variation analysis, Pd4 and Pd6 were identified as the most stable clusters. The Natural Bond Orbital (NBO) analysis and the plot of the Molecular Electrostatic Potential (MEP) – both performed for the first time – indicated that the Pd atoms in clusters were not equivalent in terms of atomic charge, population and electron configuration. The plots of the MEP mapped on the electron density also revealed its non-uniform character; areas of positive MEP were found around the Pd atoms, which may undertake nucleophilic attacks. Subsequently, the interaction of atomic oxygen with Pdn clusters was systematically studied, accounting for different possible anchoring positions. The hollow site was revealed to be the most favourable one. The increase in number of Pd atoms favoured higher spin states. Pd6O was identified as the most oxidised and energetically stable cluster. The calculated binding energy value of oxygen (3.5 eV) was in agreement with the Temperature Programmed Desorption (TPD) experimental results conducted on Pd(1 1 0) single-crystal surface. The NBO analysis evidenced that the occupancy of 2 s (2p) orbital of O decreased (increased) as the number of Pd atom increased. The negatively charged Pd atoms had a larger population of 4d orbitals than the neutral or positively charged ones. The interactions between O and Pd atoms were dominated by d-type orbitals.

Исследование взаимодействия кислорода с поверхностью боросодержащих нанотрубок

Studies of semiconductor carbon nanotubes show that they are extremely sensitive to the chemical environment, and the effects of oxygen drastically change their properties. It has been found that narrow-zone semiconductor carbon tubes can be converted into an apparent metal by such action. Since other types of nanotubes, such as boron-carbon nanotubes of the BC3 type and boron-nitride BN nanotubes, are of great interest, it seems important to investigate whether they are capable of absorbing atomic and molecular oxygen. The study was conducted using the MNDO calculation method within molecular and ion-nested covalent-cyclic cluster models. The results of the study of the interaction of atomic and molecular oxygen with the external surfaces of boron-carbon (BC3), boron-nitride (BN) and boron nanotubes are considered: chair (n, n) and zigzag (n, 0) type. The study was performed by the MNDO method as part of a covalent-cyclic cluster model with embedded ions. Optimal geometry of adsorption complexes is determined and their main electronic and energy properties are described. Boron-carbon nanotubes have been shown to be better oxygen adsorbents than other types of nanotubes considered.

Impact of the Surface and Microstructure on the Lubricative Properties of MoS2 Aging under Different Environments.

Molybdenum disulfide (MoS2) with a hydrophobic property and layered structure possesses an excellent lubricative property and has been widely used as a lubricant in various areas, including satellites, aircraft, and new energy vehicles. Aging is a ubiquitous phenomenon in MoS2 and plays a key role in its tribological application for shortening its service life. The effect of the surface and microstructure on the lubricative properties of MoS2 aging under different environments, including deionized water (DI water), ultraviolet/ozone (UV/Ozone), and high-temperature, was investigated. First, the lubrication of MoS2 transiently degrades because of physical adsorption and recovers after mechanical removal. The lubrication of MoS2 also degrades slightly when its surface becomes hydrophilic, thereby enhancing the adhesion energy due to atomic oxygen interaction under UV/Ozone exposure. Second, the lubrication of MoS2 degrades irreversibly because of the formation of stripes with the destroyed structures under accelerated aging. The lubrication of MoS2 further degrades with the formation of small triangular pits under high-temperature annealing. Finally, the lubrication of MoS2 deteriorates due to the destroyed structure and complete oxidation. The severe aging of MoS2 is accompanied with large triangular pits due to anisotropic oxidation etching of MoS2. The lubrication failure of MoS2 was determined on the basis of structural defect formation and surface property degradation induced by the extent of oxygen diffusion. The enhanced out-of-plane deformation due to the reduced out-of-plane stiffness and the increased energy barriers of defects are fundamentally responsible for the lubrication degradation of MoS2 at the atomic scale. These findings can provide new insights into the atomic-scale mechanism underlying the lubrication failure of MoS2 and pave the way for the realization of MoS2-based lubrication application under various environments.

Changes in the Surface and Volume Properties of a Spacecraft during Absorption and Recombination of Oxygen and Nitrogen Atoms

The results of studying the influence of cosmic space on a spacecraft surface is presented. We showed that the mechanical (volume and surface), optical, and other characteristics of a spacecraft’s materials noticeably change due to long exposure to cosmic vacuum. At extremely low pressures in cosmic vacuum, the external and internal interfaces in the materials can be broken, resulting in either microscopic surface cracks or internal corrosion. We have shown that changes in the properties of surface layers cause changes in the volume mechanical properties of materials (fatigue strength, etc.). Furthermore, noticeable effects of space vacuum on the mechanical properties of a spacecraft’s materials arise as a result of the absence of oxide and other surface protective films. Due to the disappearance of protective gas and oxide films, and also as a result of sublimation of the surface layers to a thickness close to the wavelengths of electromagnetic radiation, the surface roughness is changed and, as a consequence, their optical characteristics (in particular, the absorption of solar radiation and the emissivity factor) are also changed. During orbital motion in sufficiently dense layers of the upper atmosphere of the Earth, as well as under bombardment by charged particles of cosmic radiation, strong plasma-chemical loosening of the surface material of spacecraft and its dispersion into the surrounding space can occur. This process is especially evident for the front (in the direction of travel) parts of spacecraft. The method used to describe the dynamics of the interaction of atomic oxygen colliding with the surface of silicon dioxide is described. The influence of space vacuum on materials is shown. Particular attention is paid to the phenomenon of accommodation of low-orbit satellite systems and the use of information received from satellites.

Comparative study on the adsorption behaviors of O and Cl on Fe(110) surfaces with different Cr content

Joint density functional theory calculations have been performed to investigate the interactions of atomic oxygen and chlorine with the Fe(110) and Cr-doped Fe(110) surfaces both in vacuum and in aqueous solution. The results show that Cr doping on the top of surface makes the atomic oxygen adsorption more thermodynamically favorable but slightly decreases the absorbability of chlorine. Subsurface doping atom makes little contribution to the adsorption characteristics of the cases considered in this study, which indicates that doping on the first layer is a reasonable and simplified approach for studying adsorption properties on iron surfaces. The adsorption strength of O decreases on Cl pre-adsorbed surfaces, demonstrating a competition relationship between the two species. This result is consistent with the adsorption theory of passivation, which attributes Cl-induced corrosion to its inhibition of oxygen adsorption. Cr surface doping can significantly decreases the negative effects caused by chloride ion, resulting in the formation of protective oxide film.

Interaction and diffusion of atomic oxygen in monovacancy-containing Cr- and Ti-doped nickel structures

Density functional theory is used to calculate the vacancy stability and its effect on oxygen trapping and diffusion behavior in Cr- and Ti-doped nickel bulks. The calculated results show that doping of Ti and Cr has an attractive interaction with a monovacancy from the first nearest neighbor to the third nearest neighbor position. The oxygen insertion energy of the nickel perfect lattice is significantly lower than that of the doped structures. It reveals that an oxygen atom can be strongly trapped near the alloying element. A monovacancy can strongly bind with an oxygen atom, and the alloying element does not change the binding energy. The presence of Ti and Cr reduces the number of oxygen atoms, leading to a decrease in oxygen content. The overall activation energy of oxygen is increased by a monovacancy and an alloying element, which may reduce the oxygen diffusivity in the structures.

Electrostatic Discharge Threshold on Coverglass Used to Protect Solar Cells in the Low Earth Orbit

Coverglass has been widely used to cover the solar cells of solar arrays for space power generation. Coverglass with high antireflection is widely used to protect the solar arrays from performance deterioration due to irradiation of space ultraviolet, protons, electrons, atomic oxygen (AO), and so on. Along with these, thermal cycles and/or shock may accelerate the decay synergistically affecting the threshold voltage of electrostatic discharge (ESD) on the coverglass. In order to reveal the effect of aging due to AO interaction on the ESD threshold, several coverglass samples have been exposed to low earth orbit grade AO generated by the CO2 laser on the ground. Later, both pristine and AO-exposed coverglasses have been irradiated by energetic electrons to generate artificial arcing (ESD) under high vacuum system. Statistical analysis and Weibull distribution confirm that the threshold voltage of ESD is lower on the aged coverglass than virgin.

Dynamics of Graphite Oxidation at High Temperature

Interactions of ground-state atomic and molecular oxygen, O(3P) and O2(3Σg–), with a highly oriented pyrolytic graphite surface were investigated for a broad range of surface temperatures from 1100 K to approximately 2300 K. A molecular beam composed of 89% O atoms and 11% O2, with average translational energies of 472.1 and 944.4 kJ mol–1, respectively, was directed at the surface with an incidence angle, θi, of 45°. Angle- and velocity-resolved distributions were collected for nonreactively and reactively scattered products with the use of a rotatable mass spectrometer detector. Four scattered products were observed: O, O2, CO, and CO2. O atoms that exited the surface without reacting exhibited both impulsive scattering (IS) and thermal desorption (TD) components. The primary reaction product observed was carbon monoxide (CO). Carbon dioxide (CO2) was measured only with surface temperatures below 1400 K, and O2 was attributed to IS of O2 that was present in the incident beam. Although there is evidence ...

Combined method of analytical control of concentration of combustible substances with preliminary oxidization in barrier discharge

The combined method of analytical control of the concentration of combustible substances with preliminary oxidation in a barrier discharge is considered, where the analyzed substance is subjected to a combination of certain types of energy effects, which allows obtaining measurement information about the composition or physicochemical properties of the analyzed substance. In analytical practice, in a barrier discharge, ozone is synthesized in a device consisting of two coaxially located metal electrodes in the form of a tube and a rod separated by a dielectric from the pyrite glass, the gap of which is filled with air at the atmospheric pressure. The process of obtaining ozone in the device proceeds in two stages. At the first stage, endothermic dissociation of oxygen molecules occurs to atoms, and at the second (exothermic) stage, a reversible reaction of ozone formation occurs. During electro-cracking in a gaseous hydrocarbon environment in a barrier discharge, hydrocarbon molecules are splitting to the radicals. The nature of the chemical reactions and, consequently, the composition of the reaction products are determined by the initial composition of the initial substances, their pressure, as well as the time of action of the electric discharge and its power. In the interaction of atomic oxygen with the products of the electro-cracking of molecules of the analyzed substance, the balance in ozone formation is disturbed, which leads to a decrease in the ozone concentration in the barrier discharge. Changes in the concentration of ozone in the presence of vapors of liquid hydrocarbons and petroleum products in the air, directly in the ozone synthesizer, makes it possible to use the method of analytical control under consideration to determine the concentration of vapor-gas mixtures of combustible substances and petroleum products, as well as to measure saturated vapor pressure of liquid hydrocarbons, petroleum products and fuels.

Exploring the Interactions of Atomic Oxygen on Silver Clusters with Hydrogen

The interactions between AgnO− (n=1−8) and H2 (or D2) were explored by combination of the mass spectroscopy experiments and density function theory (DFT) calculations. The experiments found that all oxygen atoms in AgnO− (n=1−8) are inert in the interactions with H2 or D2 at the low temperature of 150 K, which is in contrast to their high reactivity with CO under the same condition. These observations are parallel with the preferential oxidation (PROX) of CO in excess hydrogen catalyzed by dispersed silver species in the condensed phase. Possible reaction paths between AgnO− (n=1−8) and H2 were explored using DFT calculations. The results indicated that adsorption of H2 on any site of AgnO− (n=1−8) is extremely weak, and oxidation of H2 by any kind of oxygen in AgnO− (n=1−8) has an apparent barrier strongly dependent on the adsorption style of the “O”. These experiments and theoretical results about cluster reactions provided molecule-level insights into the activity of atomic oxygen on real silver catalysts.

Interaction of Oxygen with α-Rhombohedral Boron (001) Surface

This contribution presents a computational account of strong and exothermic interaction of atomic and molecular oxygen with the α(001)B12 surface of boron. Physisorbed oxygen interacts weakly with the surface, but the dissociative chemisorption entails considerable exothermicity in the range of 2.47–3.45 eV, depending on the adsorbed sites of the two oxygen atoms. Nonetheless, rupture of dioxygen on the surface involves a sizable intrinsic reaction barrier of 3.40 eV (at 0 K). Such high amount of energy clearly explains the chemical inertness (i.e., the lack of oxidation) of boron at room temperature. However, elevated temperature encountered in real applications of boron, such as cutting machinery, overcomes the high-energy barrier for the dissociative adsorption of molecular oxygen (3.40 eV). A stability T–P phase diagram reveals the spontaneous nature of the substitutional O/α(001)B12 adsorption modes that lead to the formation of diboron trioxide (B2O3) at temperatures and pressure pertinent to practi...

Influence of CO molecular impurity on the structural and thermodynamic properties of fullerite C60, in a broad range of sorption temperatures

An x-ray diffraction study of how sorption of CO gas at a pressure of 30 atm in the temperature range of 150–600 °C influences the structural characteristics of polycrystalline and single crystal fullerite C60. The sorption kinetics are studied by constructing a dependence of the lattice parameter on the time it takes for fullerite to be saturated by CO molecules. At temperatures Tsorb > 300 °C there is an observed dissociation of carbon monoxide, accompanied by the precipitation of carbon powder and the chemical interaction of atomic oxygen with C60 and CO molecules, and possibly with the carbon condensate. These processes have a strong influence on the structural characteristics of fullerite, thus creating, in part, a nonmonotonic dependence of the parameter and lattice matrix volume on the impurity saturation temperature. The concentrations of solid solutions C60(CO)x poly- and single crystal samples are determined in the physisorption range for two modes (150 and 250 °C). It is found that the CO impurity has a linear effect on the lattice parameter and the temperature of the orientational transition of fullerite C60.

First-principles investigations of oxygen adsorption at TiNi surface and the TiO2/TiO–TiNi interface

Ab-intio study of the interaction of atomic and molecular oxygen with the TiNi(110) surface was performed using the projector augmented wave method with generalized gradient approximation for the exchange-correlation functional. The oxygen adsorption energies were calculated and the preferential adsorption sites of oxygen atom on the surface were determined. Our results confirmed the formation of a Ni-rich layer at the alloy–oxide interface. Atomic and electronic structure of both TiO/TiNi(110) and TiO2/TiNi(110) interfaces were analyzed. The formation energies (Ef) of point defects at the interfacial layers as well as in bulk TiNi, monoclinic TiO, and rutile TiO2 were estimated. It was shown that Ef of Ti–Ni swap defect has a lower energy than that for the Ni antisites at the TiO2(100)/TiNi(110) interface. In the case of TiO(100)/TiNi(110) interface, the formation energies of Ti–Ni swap and Ni-antisites defects are close to each other. Our results demonstrated that Ef of Ni-defect in TiO is twice less than that in TiO2. The increase in the formation energies of defects in TiO2 reveal the increase in diffusion barriers of Ni atoms in comparison with those in oxides with a lower oxygen content, which hampers Ni segregation.

Elementary Reaction Processes Involving Atomic and Molecular Oxygen on ZrB2 (0001) Surface

The interaction of atomic and molecular oxygen along with the atomic recombination on thin ZrB2(0001) Zr- and B-terminated surfaces were studied using density functional theory (GGA/PBE) calculations. The adsorption of atomic oxygen is predominantly produced on 3-fold hollow sites for the Zr-finished surface and on B–B bridge sites for the B-finished surface. The experimental specular HREELS loss peaks and their shifts at high O exposures can be satisfactory explained by the present calculations. The interaction of O2 over both terminated surfaces produces mainly its dissociation through nonactivated processes. This fact is in agreement with the observed open dissociation at room temperature. The atomic oxygen recombination over both ZrB2 surfaces shows that the Eley–Rideal reaction will be much more important than the Langmuir–Hinshelwood reaction at all temperatures and even more accessible in the case of the B-finished surface.

Modeling of catalytic activity of an Al2O3 surface on the basis of the first principles

The adsorption, desorption, impact, and associative heterogeneous recombination rate coefficients are determined for atomic oxygen in the temperature range between 500 and 2000 K on the basis of quantum chemical data on the energy of interaction of atomic and molecular oxygen with the clusters that model an α-Al203 surface. These coefficients are used to calculate the heterogeneous recombination probabilities and the heat fluxes to the surface under the conditions similar to those of the MESOX facility.

Reactivity and Morphology of Oxygen-Modified Au Surfaces

Inducing the adsorption of oxygen on gold surfaces transforms the inert metal into a surprisingly reactive material, which acts as a highly selective, low-temperature catalyst. The strong interaction of atomic oxygen with Au greatly affects the surface morphology by increasing the number of undercoordinated Au atoms and lifting the surface reconstruction. Through the combination of experimental and theoretical techniques, we have fully characterized an oxygen, modified Au(100) surface and determined the structure-reactivity relationship of O-Au species. Bulk-implanted oxygen does not affect the reactivity of Au surfaces and subsurface oxygen is found to be unstable. Oxygen stabilizes undercoordinated Au atoms on the surface and becomes highly active for oxidation reactions when adsorbed on unreconstructed Au(100) sites.