Existence Of Hydrogen Atoms Research Articles

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.

Low-Energy Electronic Properties of Graphene and Armchair Ribbon Superlattices

The geometric structures and electronic properties of graphene and armchair ribbon superlattices are investigated by the first-principles calculations. Parallel armchair ribbons are periodically placed upon a graphene sheet. The interlayer atomic interactions strongly influence the interlayer distance, binding energy, energy dispersion, state degeneracy, band gap, Fermi velocity, and Fermi momentum except for the intralayer bond length. These properties depend on the stacking configurations, ribbon width, and existence of hydrogen atoms at the ribbon edges. Such interactions also result in the distortion of graphene and ribbons, which is more obvious in the AA-stacked systems than the AB-stacked ones. All low-energy bands come from the 2pz orbitals of graphene or ribbon or from those of both. Most AA-stacked systems possess two intersecting low-lying bands, which exhibit highly anisotropic Fermi velocities. AB-stacked systems mainly have a direct band gap that is monotonously widened as ribbon width expands.

On the existence of hydrogen atoms in higher dimensional Euclidean spaces

The question of whether hydrogen atoms can exist or not in spaces with a number of dimensions greater than 3 is revisited, considering higher dimensional Euclidean spaces. Previous results which lead to different answers to this question are briefly reviewed. The scenario where not only the kinematical term of Schr\"odinger equation is generalized to a D-dimensional space but also the electric charge conservation law (expressed here by the Poisson law) should actually remains valid is assumed. In this case, the potential energy in the Schr\"odinger equation goes like 1/r^{D-2}. The lowest quantum mechanical bound states and the corresponding wave functions are determined by applying the Numerov numerical method to solve Schr\"odinger's eigenvalue equation. States for different angular momentum quantum number (l = 0; 1) and dimensionality (5 \leq D \leq 10) are considered. One is lead to the result that hydrogen atoms in higher dimensions could actually exist. For the same range of the dimensionality D, the energy eigenvalues and wave functions are determined for l = 1. The most probable distance between the electron and the nucleus are then computed as a function of D showing the possibility of tiny bound states.