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Molecular dynamics simulation was used to investigate the mechanical properties of (5, 5), and (10, 10) single-walled nanocoils, as well as (5, 5)@(10, 10) double-walled carbon nanocoils (CNCS). The second reactive empirical bond order potential was employed to model the interaction between carbon atoms. The atomic slip vector and sequential slip vector were used to investigate the structural variations at different strains during the tension process. The yield stress, maximum tensile strength, and Young’s modulus were determined from the tensile stress–strain profiles. The results show that the nanocoils have superelastic characteristics and have a high strength similar to that of carbon nanotube with same chirality.

The studies of silica nanoclusters are of substantial interest for large potential in applications as diverse as photonics/optics, microelectronics and catalysis. In this study, we used the basing-hopping method with Buckingham potential to get the stable structures of silica nanoclusters ((SiO2)(n) = 1-13). The global minimum geometry of silica nanoclusters were determined by density functional theory calculation. We investigated the energy gap, binding energy and second order energy difference of nanoclusters to determine their structural stability with different sizes. We also calculate the second-order energy difference, binding energy to determine the magic number.

The mechanical properties of Ni-Ta crystallizationand binary bulk metallic glasses (BMG) were investigated for this study at the nanoscale. First, the Ta9Ni3 crystals are formed by space group, and structures with different ratios (Ta1Ni1, BTa8Ni4, BTa9Ni3, BTa7Ni5) were put into unit cell randomly. The optimizations of BMG structures are performed by Density functional theory (DFT) calculation to find the stable amorphous structures and corresponding energy. The FMM is utilized to obtain the suitable parameters of tight-binding potential bystable amorphous structures and corresponding energies. Finally, we employ molecular dynamics (MD) simulation to study mechanical properties of Ni/Ta crystallization and BMG, such as atomistic stress-strain, plastic and elastic deformation, and elastic modulus.

The adsorption and dissociation properties of carbon monoxide (CO) molecule on tungsten W(n) (n = 10-15) nanoparticles have been investigated by density-functional theory (DFT) calculations. The lowest-energy structures for W(n) (n = 10-15) nanoparticles are found by the basin-hopping method and big-bang method with the modified tight-binding many-body potential. We calculated the corresponding adsorption energies, C-O bond lengths and dissociation barriers for adsorption of CO on nanoparticles. The electronic properties of CO on nanoparticles are studied by the analysis of density of state and charge density. The characteristic of CO on W(n) nanoparticles are also compared with that of W bulk.

The adsorption and dissociation of H2O in Pd nanowire have been investigated by the density functional theory (DFT) studies. First, we construct Pd nanowire by basin-hopping method and use DFT calculation to find the ground state of Pd nanowire, and put the H2O molecular on different adsorption sites and the H2O molecule is found to preferentially absorb on a Top (T) site. The H2O molecule lies parallel to the Pd nanowire surface, while the O atom is bound at a Top site. We also calculate the partial density of state (PDOS) and election density difference. In addition, our calculated results demonstrate that the bonding between H2O and Pd nanowire is contributed by d orbitals of Pd nanowire and p orbitals of O atom. The nudged elastic band (NEB) method is applied to locate transition states and minimum energy pathways (MEP), and we discuss the dissociation behavior of the side-on H2O molecules on the top site of hexagonal and tetragonal planes, respectively.

In our previous study, we have proven two ultrathin Pd nanowires can prevent from Pd embrittlement. In this study, we further demonstrate the material properties of a larger Pd nanowire. Both classical potential function and density functional theory calculation were used. The results show once the larger Pd nanowire has interior Pd atoms, hydrogen atoms can stably stay within the nanowire. Consequently, the hydrogen embrittlement could happen with a higher probability than two ultrathin Pd nanowires reported in our previous study.

CO oxidations on the surface of tungsten nanoparticle W10 and on W(111) surface were investigated by density functional theory (DFT) calculations. The molecular structures and surface–adsorbate interaction energies of CO and O2 on the W10 and W(111) surfaces were predicted. Three CO oxidation reactions of CO + O2 → CO2 + O, CO + O + O → CO2 + O, and CO + O → CO2 were considered in Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) reaction mechanisms. The nudged elastic band (NEB) method was applied to locate transition states and minimum energy pathways (MEP) of CO oxidation on the W10 and W(111) surfaces. All reaction barriers were predicted, implying the CO oxidations on both the W10 nanoparticle and W(111) surfaces prefer the ER mechanism. The electronic density of states (DOS) was calculated to understand the interaction between adsorbates and surfaces for the CO oxidation process. In this study, we have demonstrated that the catalytic ability of W10 nanoparticles is superior to that of the W(111) surfac...

The adsorption and dissociation of NH(3) on the clean and hydroxylated TiO(2) rutile (110) surfaces have been investigated by the first-principles calculations. The monodentate adsorbates such as H(3)N-Ti(a), H(2)N-Ti(a), N-Ti(a), H(2)N-O(a), HN-O(a), N-O(a) and H-O(a), as well as the bidentate adsorbate, Ti-N-Ti(a) can be formed on the clean surface. It is found that the hydroxyl group enhances the adsorption of certain adsorbates on the five-fold-coordinated Ti atoms (5c-Ti), namely H(2)N-Ti(a), HN-Ti(a), N-Ti(a) and Ti-N-Ti(a). In addition, the adsorption energy increases as the number of hydroxyl groups increases. On the contrary, the opposite effect is found for those on the two-fold-coordinated O atoms (2c-O). The enhanced adsorption of NH(x) (x = 1-2) on the 5c-Ti is due to the large electronegativity of the OH group, increasing the acidity of the Ti center. This also contributes to diminish the adsorption of NH(x) (x = 1-2) on the two-fold-coordinated O atoms (2c-O) decreasing its basicity. According to potential energy profile, the NH(3) dissociation on the TiO(2) surface is endothermic and the hydroxyl group is found to lower the energetics of H(2)N-Ti(a)+H-O(a) and HN-Ti(a)+2{H-O(a)}, but slightly raise the energetic of Ti-N-Ti(a)+3{H-O(a)} compare to those on the clean surface. However, the dissociation of NH(3) is found to occur on the hydroxylated surface with an overall endothermic by 31.8 kcal/mol and requires a barrier of 37.5 kcal/mol. A comparison of NH(3) on anatase surface has been discussed. The detailed electronic analysis is also carried out to gain insights into the interaction nature between adsorbate and surface.

The adsorption and dissociation of O2 molecules on W(111) surface have been studied at the density functional theory (DFT) level in conjunction with the projector augmented wave (PAW) method. All passable dissociation reaction paths of O2 molecule on W(111) surface are considered. The nudged elastic band (NEB) method is applied to locate transition states, and minimum energy pathways (MEP). We find that there is an existing of little barriers for the dissociations reaction of O2 molecule. Ab initio molecular dynamics simulation is also preformed to study the adsorption and dissociation mechanism of O2 molecules on the W(111) surface. Our results indicate that O2 molecule will be dissociated by inclined deposition at temperature of 10 K, but can stable adsorb on top site by normal deposition. The change of bond length and adsorption energy in process of dissociation of O2 molecules on the W(111) surface are also calculated. The O2 coverage effect is also discussed in this paper.

The scratch deformation behaviors of two bicrystal coppers (Cu(100)/Cu(110) and Cu(110)/Cu(100)) during the nanoscratching process were explored and compared with their single crystal ingredients by the molecular statics simulations. The effects of lattice configuration and scratch depth were investigated in this study. The results showed that the motion of dislocations was blocked in the bicrystal interface until the dislocations accumulated enough energy to move. From the study, it was found that the bicrystal interfaces can provide resistance to the motion of dislocations, and can strengthen the mechanical properties of copper materials.

The collective dynamic behavior of carbon atoms of a (17, 0) zigzag single wall carbon nanotube is investigated under tensile strains by molecular dynamics (MD) simulations. The “slip vector” parameter is used to study the collective motion of a group of atoms and the deformation behavior in three different directions (axial, radial, and tangential) of a (17, 0) carbon nanotube. The variations of radial slip vectors indicate almost all carbon atoms of the (17, 0) carbon nanotube will stay on the cylindrical surface before the yielding of the single wall carbon nanotube (SWNT). Furthermore, the tangential vectors show kinking deformation for the (17, 0) zigzag tube only rarely appears when the crack occurs. Non-symmetrical deformation around a carbon atom along the axial direction also can be found. The variations in the slip vector values of each atom display a symmetrical crack along the horizontal direction and normal to the tube axis. Chain-like structures with 3–4 atoms can be observed, with the number of chain-like structures decreasing before the breakage of the SWNT. The mechanical properties and dynamic behavior of a (17, 0) zigzag SWNT under tensile strain are also compared with that of a (10, 10) armchair tube in our previous study (Weng et al. 2009).

The electronic properties of an armchair (4,4) single-walled silicon carbide nanotube (SWSiCNT) with the length and diameter of 22.4 and 6.93 A, respectively under different tensile strains are investigated by density functional theory (DFT) calculation. The change of highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gap of the nanotube has been observed during the elongation process. Our results show that the gap will significantly decrease linearly with the increase of axial strain. Two different slopes are found before and after an 11% strain in the profiles of the HOMO–LUMO gap. The radial buckling has been performed to investigate the radial geometry of nanotube. The partial density of states (PDOS) of two neighboring Si and C atoms of the nanotube are further studied to demonstrate the strain effect on the electronic structure of SiC nanotube. The PDOS results exhibit that the occupied states of Si atom and the unoccupied states of C atom are red-shifted and blue-shifted under stretching, respectively. Mulliken charge analysis reveals that Si and C atoms will become less ionic under the larger strain. The electron differences of silicon carbide nanotube (SiCNT) on tensile loading are also studied.

Understanding the electronic structures and properties of different size CeO 2 nanoparticles is very important for further application in the field of catalysis used in several promising materials. In this study, we have elucidated the electronic analyses of (CeO 2 ) n ( n = 1–5) nanoparticles through first-principle density-functional theory approach. All structures with the global minimal energies are obtained by fire algorithm combining simulated annealing method and then are further re-optimized by DMol 3 program with double numerical atomic basis sets. Two useful analyzed methods (Fukui function and electronic density of state) are calculated to explain the chemical reactivity of different sites for (CeO 2 ) n ( n = 1–5) nanoparticles.

Thermodynamic properties of titanium dioxide (TiO 2 ) n ( n = 1–6) nanoparticles were studied by first-principle molecular dynamics (MD) simulation. The configurations for (TiO 2 ) n ( n = 1–6) nanoparticles with global minimum energies can be initially obtained by MD simulation combined with the fast inertial relaxation engine algorithm. These structures can be further refined by density functional theory simulation. The variation of internal energies and Lindemann criteria with the simulation temperature was used to indicate the occurring of phase change for (TiO 2 ) n ( n = 1–6) nanoparticles. The effect of size and geometry on the thermodynamic properties of TiO 2 nanoparticles was also found.

Molecular dynamics simulation is used to investigate the dynamic properties of water molecules inside an Au nanotube in different water densities. From the oxygen density profiles, some characteristic peaks appear at specific regions. In order to observe the dynamical behaviors of water molecules in different portions in the Au nanotube, these specific peaks are divided into three regions—I, II, and III—which are 0−4, 4−7, and 7−10 A, respectively, as measured from the center of the tube to the inside wall of the tube. Since the strength of hydrogen bonds between water molecules within regions I and II can overcome the interaction between the Au nanotube and the water molecules within those regions, the major peaks of the region I and II spectra are similar to those of bulk water. However, the strength of hydrogen bonds between water molecules within region III cannot overcome the interaction between the Au nanotube and the water molecules within that region, so the major peak of the region III spectrum s...

Understanding material properties of CeO2 nanoparticles of different sizes is very important for its further applications in the field of catalysis used in solid-oxide fuel cells. In this study, the fast inertial relaxation engine (FIRE) algorithm combined with the simulated annealing method was firstly employed to find the structures of (CeO2)n (n = 1–5) with global minimum potential energy. These structures were further refined by the density functional theory (DFT) simulation in order to deeply understand their structural properties.

Understanding the mechanical properties of multilayered metal thin films is very important for their applications in nanoscale devices. Nanoindentation is one of the widely used tools for examining the mechanical properties of metal thin films. In the present study, molecular dynamics simulation was employed to investigate the nanoindentation behavior of a Cu(100)/Cu(110) bilayered thin film. The load-displacement response and the detailed deformation structure of the copper thin film during the nanoindentation were inspected and compared with those of Cu(100) and Cu(110) thin films. It was found that at the indenting stage the maximum indentation load of the bi-layered thin film is lower than that of its ingredients, however, they have nearly the same maximum indentation load. At the retracting stage, the maximum attractive force of the bilayered thin film was found near that of its ingredients but occurred much earlier than the ingredients. The detailed deformation structure of the bilayered thin film was observed to be similar to that of the ingredients and correlated very well with the load-displacement response.

Molecular dynamics simulation was carried out to investigate the behavior of (5,5) and (10,10) armchair carbon nanotubes in water under tensile loading. The water molecules inside a nanoscale tube, unlike inside a bulk tube, have a confined effect. The local density distributions of oxygen and hydrogen atoms inside the carbon nanotubes were calculated to find the confinement effect. Moreover, the mechanical behavior of carbon nanotubes in water was studied under tensile loading. The results show that the Young's modulus of nano-tubes in water remains the same as that in vacuum. However, the tensile stress of nanotube in water is less than that in vacuum.

Tricarboxylic acid derivative with three-fold symmetry in physisorbed monolayers is an important organic molecule for applications in nanotechnology. In this paper, the behaviour of a single tricarboxylic acid derivative, 1,3,5-tris(carboxymethoxy)benzene (TCMB, C6H3(OCH2COOH)3) on an Au (111) substrate at 50 K is investigated by molecular dynamics simulation. Four possible conformations of the TCMB molecule adsorbed on the Au (111) substrate are found, the difference of which is the orientation of the CH2 chain. They also display different trajectories of movement and dynamical behaviours. As the molecule migrates across the Au (111) surface, the translational motion of TCMB is always accompanied by rotational motion. The lock-and-key (LAK) geometry between the TCMB molecule of different conformations and atomic arrangement of the Au (111) surface was also observed in this study, and the result has been verified by an ab initio calculation.

In recent years, the phonon spectrum has attracted much interest in investigations of electric transfer in nanowires. In this study, molecular dynamics is employed to calculate the phonon characteristics of thinness for 7-1 gold nanowire stretched at room temperature. This study finds that the two major peaks of phonon density of state (DOS) of 7-1 nanowire represent low characteristic frequency shifts to the left, while high characteristic frequency is less significant changed compared with the characteristic frequency in bulk. The high frequency intensity of DOS for 7-1 nanowire is lower than that of low frequency. The low frequency shifts left for large elastic strain during elastic deformation. Moreover, the phonon spectrums of one-atom chain structures formed before the nanowire breaks becomes discrete. The influences of local atomic arrangement and stretch condition on the phonon profile are analyzed in this study.

In this study, the molecular dynamics is employed to simulate the selfassembly of crossed gold nanowires at various temperatures. The nanowires with a multi-shell helical (HMS) structure are different from those of the bulk FCC structure. This work compares the morphology of crossed HMS nanowires with 7-1 structure after self-assembly and investigates the atom motion trajectory on the joint. The structure transform are observed from helical structure to FCC structure by angular correlation function (ACF). The results can be suggested for a nano-scale circuit design.

The phonon spectrum has in recent years attracted much interest in investigating electrical transfer in nanowires. In this study, molecular dynamics is employed to calculate the phonon property of thinness for 7-1 gold nanowire at room temperature. This study finds that the phonon density distribution of 7-1 nanowire is different from both that of bulk face-centred cubic (fcc) structure and that of nanoparticles. We also observed that the high frequency of the phonon spectrum in the bulk fcc structure has a higher intensity than the low frequency of the phonon spectrum. This phenomenon, however, does not appear in the 7-1 nanowire. The strain effect of 7-1 nanowire on the phonon property has also been studied; moreover, the phonon spectra of core–core and shell–shell structures of nanowire exhibit two different modes. The relationship between the phonon profile of these core and shell structures is analysed in this study.

The adsorption and dissociation of H2O in Pd nanowire have been investigated by the density functional theory (DFT) studies. First, we construct Pd nanowire by basin-hopping method and use DFT calculation to find the ground state of Pd nanowire, and put the H2O molecular on different adsorption sites and the H2O molecule is found to preferentially absorb on a Top (T) site. The H2O molecule lies parallel to the Pd nanowire surface, while the O atom is bound at a Top site. We also calculate the partial density of state (PDOS) and election density difference. In addition, our calculated results demonstrate that the bonding between H2O and Pd nanowire is contributed by d orbitals of Pd nanowire and p orbitals of O atom. The nudged elastic band (NEB) method is applied to locate transition states and minimum energy pathways (MEP), and we discuss the dissociation behavior of the side-on H2O molecules on the top site of hexagonal and tetragonal planes, respectively.

Molecular dynamics simulation was employed to investigate the diffusion behaviors of water molecules within a (5,5) carbon nanocoil (CNC) at different tensile strains, the length and coil diameter of CNC are 22 and 6.83 Ǻ, respectively. Condensed-phase, optimized molecular potentials for atomistic simulation studies were employed to model the interaction between atoms. The results show that the diffusion in the axial direction can be enhanced by the tensile strain and the water molecule flow can be blocked at a higher strain once the deformed areas appear at the higher strain. Moreover, the deformed (5,5) CNC at strain of 2.8 can recover its original structure at strain of 0, indicating that the adjustment of diffusion coefficient is repeatable by applying different strains in the axial direction.

The adsorption, dissociation, and diffusion of hydrogen in Ni(100) and Ni(100)/YSZ(100) slabs with two different interfaces (Ni/cation and Ni/O interface) have been studied by the density functional theory (DFT) with the Perdew-Wang functional. The H(2) molecule is found to preferentially absorb on a Top (T) site with side-on configuration on the Ni(100) surface, while the H-atom is strongly bound at a fcc Hollow (H) site. The barrier for the H(2) dissociation on both surfaces is calculated to be only ~0.1 eV. The potential energy pathways of H diffusion on pure Ni and Ni/YSZ with the two different interfaces are studied. Our calculated results show that the H-atom diffusion occurs via surface path rather than the bulk path. For the bulk path in Ni/YSZ, H-atom migration can occur more readily at the Ni/cation interface compared to the Ni/O interface. The existence of vacancy in the interface region is found to improve the mobility of H-atoms at the interface of Ni/YSZ slab. The rate constants for hydrogen dissociation and diffusion in pure Ni and Ni/YSZ are predicted.

The adsorption and dissociation of O2 molecules on W(111) surface have been studied at the density functional theory (DFT) level in conjunction with the projector augmented wave (PAW) method. All passable dissociation reaction paths of O2 molecule on W(111) surface are considered. The nudged elastic band (NEB) method is applied to locate transition states, and minimum energy pathways (MEP). We find that there is an existing of little barriers for the dissociations reaction of O2 molecule. Ab initio molecular dynamics simulation is also preformed to study the adsorption and dissociation mechanism of O2 molecules on the W(111) surface. Our results indicate that O2 molecule will be dissociated by inclined deposition at temperature of 10 K, but can stable adsorb on top site by normal deposition. The change of bond length and adsorption energy in process of dissociation of O2 molecules on the W(111) surface are also calculated. The O2 coverage effect is also discussed in this paper.

Mechanical properties of ultrathin zinc oxide (ZnO) nanowires of about 0.7-1.1 nm width and in the unbuckled wurtzite (WZ) phase have been carried out by molecular dynamics simulation. As the width of the nanowire decreases, Young's modulus, stress-strain behavior, and yielding stress all increase. In addition, the yielding strength and Young's modulus of Type III are much lower than the other two types, because Type I and II have prominent edges on the cross-section of the nanowire. Due to the flexibility of the Zn-O bond, the phase transformation from an unbuckled WZ phase to a buckled WZ is observed under the tensile process, and this behavior is reversible. Moreover, one- and two-atom-wide chains can be observed before the ZnO nanowires rupture. These results indicate that the ultrathin nanowire possesses very high malleability.

This study investigates the behavior of water molecules inside Au nanotubes by molecular dynamics. Different sizes of Au nanotubes under three temperatures for three levels of density of Au nanotube have been studied. The structure of each thermodynamic state is analyzed through the characterization of the hydrogen-bond network. An observation of the water molecule distribution reveals that the adsorption of water molecules creates shell-like formation of water near the Au nanotube wall, and such formations are found to be more pronounced within an Au nanotube. Au atoms of different sizes have an affinity for water molecules at different temperatures.

In this paper, molecular dynamics simulation is carried out to investigate the mechanical properties and dynamic behaviors of carbon nanotubes with vacancies and related defects. We have shown the Yang's modulus and tensile strength of nanotubes with vacancy-related defects are dependent on the characteristics of vacancies. Meanwhile, the phonon density of state (DOS) are used to study the vibration properties of carbon nanotubes of various types. and further determine the dynamical behavior of carbon nanotubes under different tensile strains.

The phonon spectra in 7-1 structure of gold nanowire, which is the simplest structure among possible helical multi-shell nanowire, are studied by using molecular dynamics simulations with a tight-binding many-body potential. Our simulation identifies the outer tube (shell) and inner gold-atom row (core strand) vibrational modes. Generally, atomic interactions have a stiffening force constant due to the shortening the neighbor distance in the interior atoms. The high frequency characteristics of the vibrational modes of core strand are more pronounced than that of outer shell. However, the global phonon density of states (DOS) is predominated by the outer shell modes. The results show that the vibrational frequencies of the ultrathin gold nanowires are dependent on the strain of the wire stretching. The high frequency modes gradually decrease when strain is increased.

The structures of two ultrathin Pd nanowires were predicted by the simulated annealing basin-hopping method (SABH) with the tight-binding potential. Their material properties for applications to the hydrogen economy were further examined by density functional theory (DFT) calculation and DFT molecular dynamics (DFT-MD) simulation. In terms of thermal stability, these two Pd nanowires are still very stable at temperatures as high as 400 K. For the dissociation of hydrogen molecules, results show the dissociation is almost barrierless, and their catalytic reactivity is very similar to the Pd bulk material. The thermal stability of the H atom within these Pd nanowires was also investigated by DFT-MD, with results showing that the H atom can only stay within Pd nanowires at temperatures much lower than room temperature (298 K). This phenomenon is very different from that of H atoms within Pd bulk material or other reported nanomaterials, leading to hydrogen embrittlement, the main drawback for Pd materials applications. Our results reveal that these two ultrathin Pd nanowires not only possess the same excellent catalytic activity for hydrogen molecules as the bulk Pd material or other Pd nanomaterials, but also avoid the hydrogen embrittlement plaguing Pd bulk materials, which is the main limit to its applications in such things as hydrogen purification, storage, and detection.

A molecular dynamics simulation of water molecules through a Au nanotube with a diameter of 20 A at bulk densities 0.8, 1, and 1.2 gcm(3) has been carried out. The water molecules inside a nanoscale tube, unlike those inside a bulk tube, have a confined effect. The interaction energy of the Au nanotube wall has a direct influence on the distribution of water molecules inside the Au tube in that the adsorption of the water molecules creates shell-like formations of water. Moreover, the high number of adsorbed molecules has already achieved saturation at the wall of the Au nanotube at three bulk densities. This work compares the distribution percentage profiles of hydrogen bonds for different regions inside the tube. The structural characteristics of water molecules inside the tube have also been studied. The results reveal that the numbers of hydrogen bonds per water molecule influence the orientational order parameter q. In addition, the phenomenon of a group of molecules bonded inside the tube can be observed as the number of hydrogen bonds increase.

The dynamic behaviour of a multi-shell 14-7-1 Au nanowire is investigated and compared with that of a 7-1 Au nanowire under various tensile strains. The molecular dynamics (MD) simulations performed in this study compute the frequency shift and change in intensity of the characteristic frequency peaks of the phonon density of states of the global and substructure atoms in the radial and axial directions. The results show that the frequency shift and intensity change of the characteristic frequency peaks in the strained 14-7-1 nanowire are caused by a change in the radial atomic coupling and a higher degree of structural anisotropy due to the applied strain.