Interaction Of Atomic Hydrogen Research Articles

Long-range interaction of hydrogen atoms at finite temperatures

Long-range interaction of hydrogen atoms at finite temperatures

Hydrogen interaction with vacancy defects in tungsten: Unraveling the influence on diffusion mechanisms and mechanical properties

This study investigates hydrogen diffusion in tungsten at high temperatures using molecular dynamics simulations. It explores the effect of different hydrogen concentrations on diffusion mechanisms, the interaction of hydrogen atoms with vacancy defects, and their impact on the mechanical properties of tungsten. The activation energy for hydrogen diffusion in perfect bulk tungsten with 0.1 % hydrogen concentration is calculated as 0.235 eV, with a diffusion pre-exponential factor of 5.336 × 10-8 m2/s at temperatures ranging from 1000 to 3000 K. The investigation reveals two factors contributing to the increase in activation energy with temperature: migration paths involving TIS-TIS and TIS-OIS-TIS pathways, and an increase in migration energy. Three diffusion regimes are identified, with trapping effects dominating at temperatures below 1500 K, TIS-TIS pathway dominating at intermediate temperatures, and TIS-OIS-TIS pathway becoming more prominent at higher temperatures. Increasing hydrogen concentration up to 2 % (H/W concentrations in fusion environments) has minimal effect on diffusion in perfect tungsten. However, in a W-H-V system with a 1 % vacancy defect, increasing hydrogen concentration increases the effective diffusion coefficient and activation energy. The presence of hydrogen atoms and vacancy defects reduces the tensile strength and elastic modulus of tungsten, with hydrogen atoms having a greater impact on mechanical properties compared to vacancies. The degree of reduction in mechanical properties is proportional to the concentration of hydrogen atoms and vacancy defects.

Hydrogenation of Hexa-peri-hexabenzocoronene: An Entry to Nanographanes and Nanodiamonds.

The fabrication of atomically precise nanographanes is a largely unexplored frontier in carbon-sp3 nanomaterials, enabling potential applications in phononics, photonics and electronics. One strategy is the hydrogenation of prototypical nanographene monolayers and multilayers under vacuum conditions. Here, we study the interaction of atomic hydrogen, generated by a hydrogen source and hydrogen plasma, with hexa-peri-hexabenzocoronene on gold using integrated time-of-flight mass spectrometry, scanning tunneling microscopy and Raman spectroscopy. Density functional tight-binding molecular dynamics is employed to rationalize the conversion to sp3 carbon atoms. The resulting hydrogenation of hexa-peri-hexabenzocoronene molecules is demonstrated computationally and experimentally, and the potential for atomically precise hexa-peri-hexabenzocoronene-derived nanodiamond fabrication is proposed.

Friction reactions induced by selective hydrogenation of textured surface under lubricant conditions

The passivation of hydrogen atoms and the conformation of textured surfaces under oil-lubricated conditions are effective strategies to obtain amorphous carbon (a-C) films with extremely low friction. It is critical to understanding the influence mechanism of selective surface hydrogenation on the tribological behaviors of textured a-C film under oil-lubricated conditions. In particular, the interactions of hydrogen atoms and lubricants are confusing, which is enslaved to the in situ characterization technique. The reactive molecular dynamics (RMD) simulations were conducted to analyze the friction response of textured a-C films with selective hydrogenation surfaces under oil-lubricated conditions. The results indicate that the existence of hydrogen atoms on specific bump sites significantly decreases the friction coefficient (μ) of textured a-C film, which is highly dependent on the surface hydrogen content. The repulsion between hydrogen atoms and lubricant molecules prompts the formation of a dense lubricant film on the surface of the mating material. Interestingly, with the enhancement of the surface hydrogen content, the passivation of the friction interface and the repulsion between hydrogen atoms and lubricants play dominant roles in reducing the friction coefficient instead of hydrodynamic lubrication.

Interactions of hydrogen atoms with boron and gallium in silicon crystals co-doped with phosphorus and acceptors

Reports showing that hydrogen and group-III acceptors play an important role in Light- and elevated Temperature-induced Degradation (LeTID) of Si-based solar cells highlight the need for a better understanding of interactions between these two species. In this contribution, a combination of junction spectroscopy techniques and first principles modelling has been used to study hydrogen-induced changes in electrical properties of either boron or gallium Czochralski-grown silicon co-doped with phosphorus in order to produce n-type material facilitating novel techniques to assess recombination active defects. The interactions of hydrogen with acceptor atoms have been induced via annealing of these co-doped hydrogenated samples with the application of reverse bias (RBA). These treatments have resulted in a significant increase in the net shallow donor concentration in depletion regions of both materials and in the appearance of a strong electron emission signal due to a trap with an energy level at about Ec −0.18 eV in the DLTS spectra of Si:P + B material. It is argued that this trap is related to the donor level of a BH2 complex. Calculations using density functional theory have shown that the BH2 defect has a charge-state dependent geometry, which turns out to be crucial for the proposed non-radiative recombination mechanism. The BH2 defect is therefore suggested to be the root cause of LeTID in boron-doped Si. In contrast, modelling results predict that GaH2 is a defect with shallow energy levels, without the characteristic features of a recombination centre. This is corroborated by the results of electrical measurements on hydrogenated Si:P + Ga subjected to RBA. Conventional annealing treatments were subsequently used to assess the thermal stability of acceptor-H related defects. Based on the obtained results, the peculiarities of hydrogen interactions with boron and gallium acceptors are discussed.

Peculiarities of atomic hydrogen interactions with detonation nanodiamonds

Hydrogen treatment is a popular way of surface modification of nanodiamonds. Here, we used atomic hydrogen treatment of the functionalized surface to increase its hydrophobicity gently and maintain its overall composition. Corresponding mechanism was revealed via combination of theoretical and experimental methods.

Hydrogen Trapping in Laser Powder Bed Fusion 316L Stainless Steel

In this study, the hydrogen embrittlement (HE) of 316L stainless steel produced by laser powder bed fusion (L-PBF) was investigated by means of hydrogen trapping. The susceptibility of the material to HE is strongly connected to the interaction of hydrogen atoms with volumetric defects in the material. Trapping hydrogen in those defects affects its availability to critical locations where a hydrogen-induced crack can nucleate. Therefore, it is important to study the characteristics of hydrogen traps to better understand the behavior of the material in the hydrogen environment. The hydrogen was introduced into the material via electrochemical charging, and its interactions with various trapping sites were studied through thermal desorption spectroscopy (TDS). The obtained results were compared to conventionally produced 316L stainless steel, and the correlation between microstructure, characteristics of hydrogen traps, and susceptibility to HE is discussed.

Distinguishment of Weak Interactions of Hydrogen Atoms Bound to Carbon Atoms: X-Ray Crystal Structural and Hirshfeld Surface Analyses of 2- Hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene with the 2- Methoxylated Homologue

Abstract: X-ray crystal and Hirshfeld surface analyses of 2-hydroxy-7-methoxy-3-(2,4,6- trimethylbenzoyl)naphthalene and its 2-methoxylated homologue show quantitatively and visually distinct molecular contacts in crystals and minute differences in the weak intermolecular interactions. The title compound has a helical tubular packing, where molecules are piled in a two-folded head-to-tail fashion. The homologue has a tight zigzag molecular string lined up behind each other via nonclassical intermolecular hydrogen bonds between the carbonyl oxygen atom and the hydrogen atom of the naphthalene ring. The dnorm index obtained from the Hirshfeld surface analysis quantitatively demonstrates stronger molecular contacts in the homologue, an ethereal compound, than in the title compound, an alcohol, which is consistent with the higher melting temperature of the former than the latter. Stabilization through the significantly weak intermolecular nonclassical hydrogen bonding interactions in the homologue surpasses the stability imparted by the intramolecular C=O…H–O classical hydrogen bonds in the title compound. The classical hydrogen bond places the six-membered ring in the concave of the title molecule. The hydroxy group opposingly disturbs the molecular aggregation of the title compound, as demonstrated by the distorted H…H interactions covering the molecular surface, owing to the rigid molecular conformation. The position of effective interactions predominate over the strength of the classical/nonclassical hydrogen bonds in the two compounds.

Interactions of Hydrogen Atoms with Acceptor–Dioxygen Complexes in Czochralski‐Grown Silicon

It is debated in the silicon PV community whether or not the presence of hydrogen is essential for the permanent suppression (“regeneration”) of the recombination activity of the boron–oxygen (BO) defect, which is responsible for light‐induced degradation (LID) of solar cells produced from B‐doped oxygen‐rich silicon. The BO‐LID defect has been identified as a BsO2 complex which has negative‐U properties. This study focuses on the interactions of hydrogen with the BsO2 defect to elucidate the BO‐LID regeneration mechanism. With the use of junction spectroscopy techniques, the changes in concentration of the BsO2 donor state in diodes which are fabricated on Czochralski‐grown (Cz) B‐doped Si and subjected to hydrogenation and subsequent heat treatments have been monitored. It is found that annealing of the hydrogenated Cz‐Si:B diodes in the temperature range 398–448 K under the application of reverse bias (RBA) results in nearly total disappearance of the BsO2 defect. It is argued that electrically neutral BsO2–H complexes have been formed upon the RBA treatments. According to ab initio calculations, the binding energy of H+ to BsO2− exceeds that of H+ to Bs− by at least 0.1 eV, and the resulting BsO2–H complexes are electrically inactive.

Crystallization and hydrogen absorption in a Ni32Nb28Zr30Fe10 melt spun alloy and correlation with icosahedral clusters

The crystallization and the hydrogen absorption properties of a Ni 32 Nb 28 Zr 30 Fe 10 melt spun ribbon were investigated. X-ray diffraction measurements reveal that a small fraction of the ribbon is in a crystalline state, whereas the main component is amorphous. The bulk crystallization process of the alloy ribbon occurs in two steps above 770 K, as measured by differential scanning calorimetry. At each step of the crystallization process, an unusually low activation energy of the order of 180 kJ/mol, was observed. Hydrogen absorption pressure-composition isotherms measured between 598 K and 673 K showed that the enthalpy of hydrogenation is quite high (∼85 kJ/mol), as compared to that of analogous ribbons. The isotherms of these ribbons do not exhibit any plateau, similarly to other amorphous materials, but they exhibited extremely slow kinetics for hydrogen absorption. To simulate the local atomic structure involving cluster formation in amorphous Ni 32 Nb 28 Zr 30 Fe 10 alloy, DFT-MD approach was used to construct an amorphous supercell of this alloy with 108 atoms. Calculations predicted that a fully amorphous structure of Ni 32 Nb 28 Zr 30 Fe 10 can form. The low activation energy of crystallization observed before hydrogenation is due to the presence of only 3 full icosahedra without any Ni-centered icosahedra, that could provide resistance against crystallization. Moreover, a cluster analysis of the Ni 32 Nb 28 Zr 30 Fe 10 alloy after hydrogenation showed interaction of hydrogen atoms with only two icosahedra out of four found in this case, and this could be the probable reason for the extremely slow kinetics of hydrogen absorption. • Melt spun Ni 32 Nb 28 Zr 30 Fe 10 is mainly amorphous with a minor crystalline inclusion. • Activation energy for crystallization is extremely low (180 kJ/mol). • Large quantities of hydrogen are stored with a slow kinetics. • DFT Molecular Dynamics show the alloy has poor resistance to crystallization. • Hydrogen interacts with two out of four icosahedral clusters with a slow kinetics.

Long-Range Interactions for Hydrogen Atoms in Excited D States

Pressure shifts inside an atomic beam are among the more theoretically challenging effects in high-precision measurements of atomic transitions. A crucial element in their theoretical analysis is the understanding of long-range interatomic interactions inside the beam. For excited reference states, the presence of quasi-degenerate states leads to additional challenges, due to the necessity to diagonalize large matrices in the quasi-degenerate hyperfine manifolds. Here, we focus on the interactions of hydrogen atoms in reference states composed of an excited nD state (atom A), and in the metastable 2S state (atom B). We devote special attention to the cases n=3 and n=8. For n=3, the main effect is generated by quasi-degenerate virtual P states from both atoms A and B and leads to experimentally relevant second-order long-range (van-der-Waals) interactions proportional to the sixth inverse power of the interatomic distance. For n=8, in addition to virtual states with two states of P symmetry, one needs to take into account combined virtual P and F states from atoms A and B. The numerical value of the so-called C6 coefficients multiplying the interaction energy was found to grow with the principal quantum number of the reference D state; it was found to be of the order of 1011 in atomic units. The result allows for the calculation of the pressure shift inside atomic beams while driving transitions to nD states.

Interactions of hydrogen with zirconium alloying elements and oxygen vacancies in monoclinic zirconia

Using Density Functional Theory with hybrid functionals, we calculate the interactions of hydrogen atoms with some point defects in monoclinic zirconia. We consider Nb and Sn substitution for Zr atoms as well as oxygen vacancies, the latter being the main defects present in the zirconia layer. They are formed during the corrosion of zirconium claddings in pressurized water reactors. We consider various charges for the complexes formed by hydrogen atoms and the aforementioned defects. The formation and binding energies are thus expressed as functions of the Fermi level in zirconia. We find that there is almost no interaction between H and Sn atoms, while a small but noticeable binding exists between H and Nb atoms. Conversely, hydrogen atoms bind strongly to oxygen vacancies which can accommodate up to 2 hydrogen atoms. We observe that there is a range of Fermi levels where the actual stable form of hydrogen is the H2 molecule and not isolated hydrogen ions. We integrate the calculated energies in a thermodynamical model to calculate the concentrations of the various forms of hydrogen. We observe that the driving parameters are the oxygen vacancy to hydrogen ratio and the temperature. There is a change in the main stable hydrogen species upon decrease of the vacancy concentration from hydrogen trapped in vacancies to interstitial forms of hydrogen. These results provide a possible rationale for the variation of hydrogen diffusion coefficient through the oxide layer observed experimentally in literature.

Molecular dynamics approach on intermolecular interaction between n-icosane and gemini surfactant assisted nanoparticles

Wax molecules tend to aggregate, and form wax solid at low temperature and result in a wax deposition. Chemical wax inhibitors are introduced to prevent wax deposition. However, the performance of chemical wax inhibitors is temperature dependent. Computational method using Molecular Dynamics (MD) simulation is used in this research to investigate how temperature affects wax inhibition using 2,5,8,11 Tetramethyl 6 dodecyn-5,8 Diol Ethoxylate Gemini surfactant (GS) and nanoparticles silicon dioxide (NP1), tin oxide (NP2), and nickel oxide (NP3). Wax-wax interaction of H58⋯H61of n-icosane and wax-solute interaction of hydrogen atom from n-icosane wax and carbonyl oxygen atoms from GS and NPs was investigated via radial distribution function analysis (rdf). The findings revealed that GS/NPs blends have a better chance of wax inhibition than corresponding individuals. Besides that, wax-wax interaction was strongest at 288K, indicating the higher chances of wax formation at low temperature. MD simulation is a promising tool for identifying atoms responsible for the wax formation and inhibition and can be used for chemical wax inhibitor screening for different temperature.

Investigation of the adsorption behavior of two anticancer drugs on the pristine and BN-doped graphdiyne nanosheet: A DFT-D3 perception

Hydroxyurea (HU) and 5-Fluorouracil (FU) are well-known drugs that are widely used in the treatment of cancers. Interaction of the HU and FU molecules on the pristine graphdiyne (GDY) and BN-doped graphdiyne (BNGDY) nanosheet was evaluated by density functional theory (DFT) method in gas and solution phases. Various adsorption sites of GDY/BNGDY have been examined for different HU/FU drug orientations. The results indicate that the 18-membered ring area and top of the acetylenic linkage are the most suitable sites, unlike the hexagonal ring. The S1, S6, S8, and S10 structures are the most stable configurations for GDY/HU, GDY/FU, BNGDY/HU, and BNGDY/FU with the highest Eads about −0.598, −0.417, −1.289, and −0.603 eV in the gas phase and −0.960, −0.592, −1.599 and −1.485 eV in solution phase, respectively. For GDY + HU/FU, the highest Eads is due to interaction of hydrogen atom of drug with GDY; while, in BNGDY+HU/FU, the oxygen atom of drug interacts effectively with the boron atom of the sheet. Likewise, in GDY complexes, charge transfer occurs from sheet to drug, but it is inverse in BNGDY complexes. The band gap values of the GDY and BNGDY are 0.470 and 0.486 eV, respectively, that drug adsorption decreases them in the range of 2.34 to 22.43%. Adsorption behavior of the structures is further discussed and interpreted using quantum molecular descriptors, band structure, and PDOS diagrams. Recovery time values show that in the field of targeted drug delivery and nanomedicine, GDY and BNGDY are more suitable as carrier for the HU and FU drugs, respectively.

Methods of theoretical calculations and of experimental researches of the system atomic hydrogen – metal

All the main directions of energy development suggest or already implement the use of hydrogen. In addition, the interaction of low-energy hydrogen atoms with metals is also of considerable interest, both from the point of view of fundamental research and in connection with the operation of large tokamaks and thermonuclear reactors. The paper presents a literature review of the features of the interaction of hydrogen with metals.It is shown that metal-hydrogen reactions, which lead to the formation of metal hydrides, are considered as a special type of such interaction.Modern methods of experimental study of heterogeneous reactions, topochemistry of metal - hydrogen reactions, dependences of the rate of interaction on pressure and temperature are considered, models of surface processes occurring during the interaction of hydrogen with a metal are discussed.A kinetic method for studying the mechanism of interaction of atomic hydrogen with hydride-forming metals is proposed.

The mechanism of hydrogen-accelerated melting of polycrystalline copper

We investigate the melting process of polycrystalline copper doped with hydrogen atoms by using the newly developed Cu/H ReaxFF force field. Hydrogen atoms are found to effectively promote the melting of copper, and even make it happen at temperatures below the equilibrium melting temperature of copper during rapid heating. The enhanced melting is closely relevant to the interaction of hydrogen atoms with the grain boundary. We find that host Cu atoms perform cooperative vibration around the grain boundaries as the precursor of premelting. The doping of hydrogen atoms is shown to drive the vibration more violent so that the grain boundary becomes broader and the premelting is prematurely triggered. Meanwhile, hydrogen atoms segregated in grain boundaries massively diffuse into the bulk region with increasing temperature, resulting in intensification of lattice distortion of the bulk phase. This facilitates the rapid advancement of the liquid-solid interface during melting in contrast to the slow and discontinuous interface advancement in hydrogen-free polycrystalline copper. Our results suggest that even a small amount of hydrogen atoms is expected to significantly affect the thermodynamic properties of metals with the existence of structural defects.

Not all platinum surfaces are the same: Effect of the support on fundamental properties of platinum adlayer and its implications for the activity toward hydrogen evolution reaction

The adsorption of atomic hydrogen on a platinum monolayer supported on orthorhombic Mo2C(100) surface has been investigated, considering different hydrogen surface coverages. Calculations have been performed using density functional theory with the Perdew–Burke–Ernzerhof exchange correlation functional and a D3 van der Waals corrections. The theoretical insight has been gained into atomic hydrogen interaction with Pt monolayer, supported on both molybdenum and well-studied tungsten carbide, and considering hydrogen surface coverage. Fundamental properties of Pt adlayer depend on the support, affecting hydrogen evolution activity of the resulting systems. At low hydrogen coverage all systems, with the exception of Pt supported on the molybdenum-terminated Mo2C, adsorb H comparably to a pristine Pt(111) surface and their high activity for the hydrogen evolution reaction is predicted. At higher coverages supported Pt monolayers interact with atomic hydrogen unlike the Pt(111), suggesting that the activity of the supported and unsupported platinum toward hydrogen evolution reaction have different origins. Furthermore, the position of the supported platinum monolayers on the volcano curve is a function of the surface coverage, more so than for extended metal surfaces. Therefore, hydrogen surface coverage is a key variable to understand the catalytic potential, approaching towards an improved model for screening of electrocatalytic systems.

Mechanisms of hydrogen atom interactions with MoS2 monolayer

The mechanisms of H atoms interactions with single-layer MoS2, a two-dimensional transition metal dichalcogenide, are studied by static and dynamic DFT (density functional theory) modeling. Adsorption energies for H atoms on MoS2, barriers for H atoms migration and recombination on hydrogenated MoS2 surface and effects of H atoms adsorptions on MoS2 electronic properties and sulfur vacancy production were obtained by the static DFT calculations. The dynamic DFT calculations give insight into the dynamics of reactive interactions of incident H atoms with hydrogenated MoS2 at H atoms energies in the range of 0.05–1 eV and elucidate the competitive mechanism of hydrogen adsorption and recombination that limits hydrogen surface coverage at the level of 30%. Various pathways of S-vacancies production and H atoms losses on MoS2 are calculated and the effects of MoS2 temperature on these processes are estimated and discussed.

Hydroxylated Mg-rich Amorphous Silicates: A New Component of the 3.2 μm Absorption Band of Comet 67P/Churyumov–Gerasimenko

Abstract The VIRTIS imaging spectrometer on board Rosetta has shown that the nucleus surface of comet 67P/Churyumov–Gerasimenko (67P/CG) is characterized by a broad absorption band at around 3.2 μm. The feature is ubiquitous across the surface and its attribution to (a) specific material(s) has been challenging. In the present Letter, we report an experimental investigation showing that the interaction of hydrogen atoms with Mg-rich amorphous silicates determines the formation of hydroxyl groups. The resulting IR spectrum exhibits a broad feature around 3.2 μm similar to that of comet 67P/CG. Hapke’s radiative transfer model was employed to estimate an upper limit contribution of 65% of hydroxylated silicates to the observed cometary band intensity. The presence of a hydroxylated fraction in silicates on the cometary surface would represent an evolutionary link between primitive objects of the solar system and dust in the interstellar medium (ISM), where silicate grains can be hydroxylated after having interacted with hydrogen atoms. This link is consistent with the detection of the aliphatic organics in 67P/CG that also originate in the ISM.

Atomic hydrogen interactions with small polycyclic aromatic hydrocarbons cations

When exposed to a thermal beam of hydrogen atoms, gas-phase coronene cations C24H12+ can be sequentially hydrogenated. This process is accompanied by a gradual transition of the electronic structure from aromatic to aliphatic. The planar very stable coronene structure transforms into the significantly weaker corrugated structure, typical for aliphatic molecules. In this study, we have investigated the hydrogenation of 5 smaller polycyclic aromatic hydrocarbon cations using a combination of radiofrequency ion trapping with time-of-flight mass spectrometry. Anthracene (C14H10+), pyrene (C16H10+), triphenylene (C18H12+), tetracene (C18H12+) and 8-9-benzofluoranthene (C20H12+) only cover a small mass range, but differ in carbon/hydrogen ratio, number of outer-edge sites and overall structure. We have observed qualitatively similar initial hydrogenation patterns for all 5 molecular ions, with odd hydrogenation states being dominant. Strong quantitative differences in hydrogenation and in attachment-induced fragmentation were found. For the case of pyrene cations, we have also investigated exposure to atomic D. Clear lines of evidence for HD/D2 abstraction reactions of Eley–Rideal type were found, as previously observed for coronene cations.Graphical abstract