Collision of hydrogen atom with single-walled carbon nanotube: Adsorption, insertion, and healing

Engineering of Hydrogenated (6,0) Single-Walled Carbon Nanotube under Applied Uniaxial Stress: A DFT-1/2 and Molecular Dynamics Study

Herein, we systematically studied the electronic, optical, and mechanical properties of a hydrogenated (6,0) single-walled carbon nanotube [(6,0) h-SWCNT] under applied uniaxial stress from first-principles density functional theory (DFT) and molecular dynamics (MD) simulation. We have applied the uniaxial stress range from -18 to 22 GPa on the (6,0) h-SWCNT (- sign indicates compressive and + indicates tensile stress) along the tube axes. Our system was found to be an indirect semiconductor (Γ-Δ), with a band gap value of ∼0.77 eV within the linear combination of atomic orbitals (LCAO) method using a GGA-1/2 exchange-correlation approximation. The band gap for (6,0) h-SWCNT significantly varies with the application of stress. The indirect to direct band gap transition was observed under compressive stress (-14 GPa). The strained (6,0) h-SWCNT showed a strong optical absorption in the infrared region. Application of external stress enhanced the optically active region from infrared to Vis with maximum intensity within the Vis-IR region, making it a promising candidate for optoelectronic devices. Ab initio molecular dynamics (AIMD) simulation has been used to study the elastic properties of the (6,0) h-SWCNT which has a strong influence under applied stress.

First-Principle Study of Atomic Hydrogen Interaction with a Fluorinated Corannulene Radical

In this work, we study fluorination effects on atomic hydrogen interactions with the fluorinated corannulene radical (C15H10F5), which was built as a model for a partially fluorinated nanotube (or fullerene). Complete active space self-consistent field and multi-reference configuration interaction methods are employed to calculate the potential energy surfaces for both ground and excited electronic states, and the R-matrix quantum dynamics method is used to investigate the atomic hydrogen transmission and reflection dynamics through the five-membered ring in the fluorinated corannulene radical, which includes resonance effects as well as non-adiabatic transitions between the ground and excited electronic states. We also investigate hydrogen adsorptions at two sites in the middle five-membered ring, namely, on top of a carbon atom and in the middle of a carbon–carbon bond. We found that on carbon-top site, the adsorption is almost barrierless, whereas in the middle bond site, there is a barrier to hydrogen adsorption.

Quantum mechanical study of atomic hydrogen interaction with a fluorinated boron-substituted coronene radical

In this work we study the transmission of atomic hydrogen across a fluorinated boron-substituted coronene radical (C(19)H(12)BF(6)) as a model for partially fluorinated and boron-doped nanotubes or fullerenes. Complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods are employed to calculate the potential energy surfaces for both ground and excited electronic states, and one-dimensional R-matrix propagation is utilized to investigate the transmission/reflection dynamics of atomic hydrogen, through the central six-member ring of the fluorinated boron-substituted coronene radical. The quantum scattering includes resonance effects as well as non-adiabatic transitions between the ground and excited electronic states. Within the sudden approximation, both centre and off-centre approach trajectories have been investigated. Implications for atomic hydrogen encapsulation by carbon nanotube and fullerene are discussed.

Quantum study of Eley-Rideal reaction and collision induced desorption of hydrogen atoms on a graphite surface. I. H-chemisorbed case

Collision induced (CI) processes involving hydrogen atoms on a graphite surface are studied quantum mechanically within the rigid, flat surface approximation, using a time-dependent wave packet method. The Eley-Rideal (ER) reaction and collision induced desorption (CID) cross sections are obtained with the help of two propagations which use different sets of coordinates, a "product" and a "reagent" set. Several adsorbate-substrate initial states of the target H atom in the chemisorption well are considered, and CI processes are studied over a wide range of projectile energy. Results show that (i) the Eley-Rideal reaction is the major reactive outcome and (ii) CID cross sections do not exceed 4 A2 and present dynamic thresholds for low values of the target vibrational quantum number. ER cross sections show oscillations at high energies which cannot be reproduced by classical and quasiclassical trajectory calculations. They are related to the vibrational excitation of the reaction products, which is a rather steep decreasing function of the collision energy. This behavior causes a selective population of the low-lying vibrational states and allows the quantization of the product molecular states to manifest itself in a collisional observable. A peak structure in the CID cross section is also observed and is assigned to the selective population of metastable states of the transient molecular hydrogen.

Hydrogen adsorption on graphite (0001) surface: A combined spectroscopy–density-functional-theory study

The adsorption of H/D atoms on the graphite (0001) surface is investigated by means of both high-resolution electron-energy loss spectroscopy (HREELS) and periodic first-principle density-functional theory. The two methods converge towards two modes of adsorption: adsorption in clusters of about four hydrogen atoms and adsorption in pairs of atoms on contiguous carbon sites. The desorption energies estimated from the calculated dissociation energies range from 8 to 185 kJ mol(-1) leading to an estimated surface coverage at saturations of 30-44 at. %. These results are compared with previous thermal desorption spectroscopy results. New HREEL signal assignments are proposed based on quantum calculations.

Interactions between Polymers and Carbon Nanotubes: A Molecular Dynamics Study

We used force-field-based molecular dynamics to study the interaction between polymers and carbon nanotubes (CNTs). The intermolecular interaction energy between single-walled carbon nanotubes and polymers was computed, and the morphology of polymers adsorbed to the surface of nanotubes was investigated. Furthermore, the "wrapping" of nanotubes by polymer chains was examined. It was found that the specific monomer structure plays a very important role in determining the strength of interaction between nanotubes and polymers. The results of our study suggest that polymers with a backbone containing aromatic rings are promising candidates for the noncovalent binding of carbon nanotubes into composite structures. Such polymers can be used as building blocks in amphiphilic copolymers to promote increased interfacial binding between the CNT and a polymeric matrix.