Spin-polarized first-principles calculations have been conducted to study the electronic structures and magnetic properties of O and S functionalized zigzag aluminium nitride (AlN) nanoribbons. Chemical functionalization with O atoms at the edges strengthens the half-metallic properties of the AlN by adding new electronic states at the Fermi level for one spin-channel and widening the gap of the other. On the contrary, edge-termination with S atoms renders the AlN ribbon a semiconductor. Peierls instabilities towards the dimerization and trimerization of the doping atoms were observed.

We consider finite size effects on energy transfer between nanoparticles mediated by quantum systems. The nanoparticles are considered as heat reservoirs with a finite number of modes. An expression for the quasi-static energy transport between the heat reservoirs having a finite mode frequency spacing Δ is derived. The resulting equations describing long-term (t ≥1/Δ) relaxation for the mode temperatures and the average temperatures of the nanoparticles are solved. The solutions depend on small number of measurable parameters and show unusual peculiarities in their temporal variations. As is shown, Fourier’s law in a chain of identical subsystems (nanoparticles) can be validated only on a short time scale. For a larger times, when t ∼ 1/Δ, the temperatures of different modes deviate from each other, thus preventing thermal equilibrium in each subsystem, and the validity of Fourier’s law cannot be established.

Initiated Chemical Vapor Deposition (iCVD) is a well-known method for depositing polymers that are used in chemical, biological, and electrical applications. It is a variation of hot filament deposition and can used to produce conformal coatings of polymer films at relatively low reaction temperatures. It is also a solventless technique in which thin polymeric films are deposited by introducing controlled ratios of monomer and initiator gasses into the reaction chamber. Low temperatures in the reaction chamber allow the deposition of polymer films on a wide variety of substrates that include biological substrates.

We have simulated the growth of a monolayer of polymer films on two-dimensional surfaces using Monte Carlo simulation. We saw the formation of polymer chains over a time scale on the order of microseconds. We have assumed the substrate to be at room temperature while the reactor pressure close of 800 mTorr.

The grid on which we have simulated this polymer growth is represented by a 100x100 matrix, on which a series of specialized functions are executed in each time-step, or iteration. These functions can be divided into three categories: population, translation, and polymerization.

The goal of this simulation is to observe the initial growth of the iCVD surface reaction. We have obtained favorable results with the simulation and we are now looking to compare these results with experimental results for initiation growth.

Copper nanoparticles are synthesized successfully through chemical reduction of different copper salts stabilized by Ocimum Sanctum Leaf extract, a natural biopolymer. The resulting copper nanoparticles are characterized by using UV Visible Absorption Spectrometer, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Small Angle X-ray Scattering (SAXS) and Fourier Transform Infrared Spectroscopy (FTIR) experiments. Copper nanoparticles prepared display an absorption peak at around 558 nm. X-ray diffraction analysis shows that the particles are FCC crystalline. SEM and TEM display the formation of copper nanoparticles with an average size of 10 nm. The SAXS studies demonstrate the formation of spherical nanoparticles with bimodal size distribution. The FTIR spectrum analysis has confirmed the presence of functional groups of stabilizer Ocimum Sanctum leaf extract in capping the copper nanoparticles.

The electronic properties of the interface between Rh clusters and CeO2 (111), (110) and (100) surfaces were studied using an isothermal-isobaric (NPT) ensemble at 773 K and 101.343 kPa using the tight binding-quantum chemical molecular dynamics (TB-QCMD) method. The amount of electronic exchange by interaction at the interface between the supported Rh55 clusters and each CeO2 surface was investigated quantitatively. A comparison of the mean square displacement (MSD) showed that the topmost oxygens on the Rh-supporting CeO2 surface exhibited higher mobility than those of the bare CeO2 surface. Although the mobility of the topmost oxygens on the bare CeO2 surface was in the order (100) > (110) > (111), this sequence was altered by the presence of Rh, so that the oxygen mobility for the more open (110) surface was the largest. The amount of electron exchange that occurred between Rh and the CeO2 (110) surface was also larger than for the (111) or (100) surface. The Ce 4f orbitals on the CeO2 (110) surface exhibited the strongest mixing with Rh 4d orbitals, which simultaneously caused restructuring and instability of the topmost Ce-O bonds. This enhancement of oxygen migration in the presence of Rh was occurred together with an increase in the number of oxygen vacancies on the ceria surface. This was because the topmost oxygens was shifted to have a stronger affinity with Rh and thus formed stronger bonds with Rh than with Ce.

The exchange of the extra-framework Na+ ions in Engelhard titanosilicate (ETS-10) with Ag+ and Ru3+ has been investigated theoretically by means of density functional theory (DFT) and experimentally, with the aim of elucidating its effects on the structural, electronic and vibrational properties of the Ti-O-Ti quantum wire. A comparison of theoretical findings and experimental Raman data in the region of Ti-O-Ti stretching reveals that the introduction of the Ag+ ions preserves the integrity of the wire to a large extent while Ru3+ ions cause large-scale distortions along with some loss in crystallinity.

In the study of grain boundary migration of metallic materials using molecular dynamics simulation (MDS), grain boundary mobilities and activation energies are often found to be different from experimentally observed values. To reconcile the discrepancies, tremendous effort has been made to replicate experiment conditions in MDS, e.g.as low a driving force as possible, near zero grain boundary velocity. In the present study, we propose an analytic method that removes effects from non-physical conditions such as high driving force or high temperature. The analytic model presumes that two types of rate limiting events coexist during grain boundary migration. Kinetics parameters, such as activation energies, of the rare events are different and therefore should be modeled separately. Activation energies from this model are closer to experiment than previously reported values. Further, by analyzing the evolution of atomic structures, these two types of rate limiting events correspond to shear coupled migration and grain boundary sliding mechanisms, respectively.

Structure prediction for novel materials requires computationally inexpensive lattice relaxation methods. Prediction of the band gap and excited state properties depends on the accuracy of the relaxations and the sensitivity of the band edges to structural parameters. We examine the relaxation performance of common relaxation methods for several members of the type IB3-V-VI4 copper chalcogenide semiconductors, which have become of recent interest for potential photovoltaic and thermoelectric applications. These materials are members of a larger family of materials, composed of type IB and type VI elements and additional elements acting as cations, which contains structures as complex as Cu12Sb4S13 (tetrahedrite) and may benefit from materials prediction studies. Examining Cu3PS4, Cu3PSe4, Cu3AsS4, and Cu3AsSe4, we find that relaxation induced structural errors cause subsequently calculated band gap values Eg to deviate by as much as 0.6 eV from values obtained using experimentally determined structures. Using the HSE06 hybrid functional we find that the complex V/VI* anti-bonding character of the conduction band minimum creates a band gap sensitivity of order 10 eV/Å to the mean V-VI distance 〈V-VI〉. A weaker correlation between Eg and 〈IB-VI〉 exists due to the Cu-d/Ch-p* character of the valence band maximum (Ch = S, Se). Type IB-III-VI2 materials are known to have similar properties and we include CuInSe2, CuAlS2, and CuAlSe2. Regarding structural relaxation accuracy, we find that GGA+U and meta-GGA functional MS2 typically perform better than GGA (PBE) or PBEsol, but not as well as the much more expensive HSE functional.