Modern Physics Letters B

Understanding the acid-base interactions is important in chemistry, biology and material science as it helps to rationalize materials properties such as interfacial properties, wetting, adhesion and adsorption. Quantitative relation between changes in enthalpy (ΔH) and frequency shift (Δν) during the acid-base complexation is particularly important. We investigate ΔH and Δν of twenty-five complexes of acids (methanol, ethanol, propanol, butanol and phenol) with bases (benzene, pyridine, DMSO, Et₂O and THF) in CCl₄ using intermolecular perturbation theory calculations. ΔH and Δν of complexes of all alcohols with bases except benzene fall in the range from -14 kJ mol^-1 to -30 kJ mol^-1 and 215 cm^-1 to 523 cm^-1, respectively. Smaller values of ΔH (-2 kJ mol^-1 to -6 kJ mol^-1) and Δν (23 cm^-1 to 70 cm^-1) are estimated for benzene. Linear correlations are found between theoretical and experimental values of ΔH as well as Δν. For all the studied complexes, ΔH varies linearly (R² ≥ 0.97) with Δν concurrent with the Badger–Bauer rule yielding the average slope and intercept of 0.053(± 0.002) kJ mol^-1 cm and 2.15(± 0.56) kJ mol^-1, respectively.

Ethylene spark ignition experiments were conducted based on an variable energy igniter at the inflow conditions of Ma = 2.1 with stagnation state T₀ = 846 K, P₀ = 0.7 MPa. By comparing the spark energy and spark frequency of four typical operation conditions of the igniter, it is indicated that the spark energy determines the scale of the spark and the spark existing time. The spark frequency plays a role of sustaining flame and promoting the formation and propagation of the flame kernel, and it is also the dominant factor determining the ignition time compared with the spark energy. The spark power, which is the product of the spark energy and spark frequency, is the key factor affecting the ignition process. For a fixed spark power, the igniter operation condition of high spark frequency with low spark energy always exhibits a better ignition ability. As approaching the lean fuel limit, only the igniter operation condition (87 Hz and 3.0 J) could achieve a successful ignition, where the other typical operation conditions (26 Hz and 10.5 J, 247 Hz and 0.8 J, 150 Hz and 1.4 J) failed.

Velocity inversion is an interesting phenomenon of nanoscale which means that the velocity near the wall is greater than that of center. To solve this problem, fluid flow in nanochannel attracts more attention in recent years. The physical model of gas flow in two-dimensional nanochannel was established here. To describe the process with conventional control equations, Navier–Stokes equations combined with high-order accurate slip boundary conditions was used as mathematical model. With the introduction of new dimensionless variables, the problem was reduced to an ordinary differential equation. Then it was analytically solved and investigated using homotopy analysis method (HAM). The results were verified by comparing with other available experiment data. Result shows that the proposed method could predict velocity phenomenon.

In the present work, we have performed first principles calculations to study the structural and electronic properties of the MgFBr_xCl_1-x quaternary alloys using the pseudo-potential plane wave approach within the framework of density functional theory. By using the optimized initial parameters, we have obtained the physical quantities such as equilibrium lattice constants a and c, cohesive energy and band gap and then fitted the results by a quadratic expression for all x compositions. The results of bulk modulus exhibit nearly linear concentration dependence (LCD) but other quantities show nonlinear dependence. Finally, we have calculated the total and angular momentum decomposed (partial) density of states and determined the contributions of different orbitals of each atoms.

By adopting density functional theory in combination with nonequilibrium Green's functions, we investigated the electronic structure and transport properties of silicon/nitrogen (Si/N) co-doping armchair graphene nanoribbons (AGNRs) with SiN_x co-dopant incorporated in neighboring carbon atoms. The results demonstrate that the electronic structure can be modulated by introducing SiN_x co-dopants in AGNRs. The striking negative differential resistance behaviors in the range of low bias can be observed in Si/N co-doped AGNR devices. These remarkable properties suggest the potential application of Si/N co-doping AGNRs in molectronics.

Using a thin-film approach to the time-dependent Ginzburg–Landau theory, we have studied the magnetization and order parameter profile in a thin mesoscopic superconductor in the so-called SQUID geometry. Our sample is circular with a hole at the center connected to the outer rim by a very thin slit. We have also studied the influence of the boundary conditions in the thin slit on the magnetization curve of the sample.

In this paper, a plasmonic analogue of electromagnetically induced transparency (EIT) is demonstrated theoretically in a T-shaped silver nanohole array. A sharply narrow reflectance transparency window is clearly observed within the background spectrum of the broad dipole-like resonance at optical frequencies when structural asymmetry is introduced. Furthermore, the transparency peak exhibits highly sensitive response to the refractive index of surrounding medium and yield a sensitivity of 725 nm/refractive index unit (RIU), which ensures our proposed nanohole array as an excellent plasmonic sensor. In addition, the dependence of figure of merit (FOM) on structural asymmetry is investigated numerically to optimize the sensing performance of the EIT-based sensor.

Single phase MgTi₂O₄ compound was synthesized by spark plasma sintering (SPS) method. The temperature dependence of the magnetic susceptibility and specific heat measurements show that MgTi₂O₄ takes place in phase transition at 258 K. Magnetic entropy measurements show that the change of magnetic entropy ΔS_M is positive and ΔS_M increases more quickly than H^2/3 near the transition; while ΔS_M is negative and |ΔS_M| (the absolute value) increases slowly with applied field increasing at lower temperature. The change of ΔS_M at different temperature range is suggested to be related not only to spin entropy change, but also orbital entropy change. The magnetic phases of MgTi₂O₄ are suggested to be Pauli paramagnetic, collinear antiferromagnetic and non-collinear antiferromagnetic order with temperature decrease.