Modern Physics Letters B

A hierarchy of integrable nonlinear differential-difference equations associated with a discrete $3\times 3$ matrix spectral problem is proposed based on the discrete zero-curvature equations. Then, Hamiltonian structures for this hierarchy are constructed with the aid of the trace identity. Infinitely many conservation laws of the hierarchy are derived by means of spectral parameter expansions.

Polaron properties such as the binding energy and the effective mass are calculated in the fractional dimensional space approach using the second-order perturbation theory. The effect of carrier density on the static screening correction of the electron–phonon interaction is included in the Hubbard’s local field factor. It is found that the polaron properties decrease with increase in dimension due to quantum confinement. Since the screening of the electron–phonon interaction is enhanced with increase in doping, the polaron properties decrease with increasing density.

In this paper, we investigate a Bogoyavlenskii–Kadomtsev–Petviashili equation, which can be used to describe the propagation of nonlinear waves in physics, biology and electrical networks. We find that the equation is Painlevé integrable. With symbolic computation, Hirota bilinear forms, solitary waves and multi-front waves are derived. Elastic collisions between/among the two and three solitary waves are graphically discussed, where the waves maintain their shapes, amplitudes and velocities after the collision only with some phase shifts. Inelastic collisions among the multi-front waves are discussed, where the front waves coalesce into one larger front wave in their collision region.

In a multivalent salt solution, a segment of DNA is modeled as an elastic rod subjected to the interfacial traction. The shooting method is used to calculate the equilibrium configurations of condensed DNA under the action of the longitudinal end-force and interfacial traction simultaneously. The results show that the shapes of DNA are mainly determined by the competition between the interfacial energy and elastic strain energy of stretching. The change of end-to-end distance with the longitudinal end-force is consistent with the worm-like chain (WLC) model. The higher the concentration is, the stronger the condensation of DNA.

In this paper, the intrinsic point defects in ZnO crystal have been studied by the approach that integrates first-principles, thermodynamic calculations and the contributions of vibrational entropy. With temperature increasing and oxygen partial pressure decreasing, the formation energies of oxygen vacancy $({\mathrm{\text{V}}}_{\mathrm{\text{O}}})$, zinc interstitial $({\mathrm{\text{Zn}}}_{\mathrm{\text{i}}})$ and zinc anti-site $({\mathrm{\text{Zn}}}_{\mathrm{\text{O}}})$ are decreasing, while it increases for zinc vacancy $({\mathrm{\text{V}}}_{\mathrm{\text{Zn}}})$, oxygen interstitial $({\mathrm{\text{O}}}_{\mathrm{\text{i}}})$ and oxygen anti-site $({\mathrm{\text{O}}}_{\mathrm{\text{Zn}}})$. They are more sensitive to temperature than oxygen partial pressure. There are two interesting phenomena. First, ${\mathrm{\text{V}}}_{\mathrm{\text{O}}}$ or ${\mathrm{\text{V}}}_{\mathrm{\text{Zn}}}$ have the lowest formation energies for whole Fermi level at special environment condition (such as at $T=300\mathrm{\text{K}}$, about $P_{\mathrm{\text{O}}2}=10^{-10}\mathrm{\text{atm}}$ or $T=1500\mathrm{\text{K}}$, about $P_{\mathrm{\text{O}}2}=10^4\mathrm{\text{atm}}$) and intrinsic $p$-type doping of ZnO is possible by ${\mathrm{\text{V}}}_{\mathrm{\text{Zn}}}$ at these special conditions. Second, ${\mathrm{\text{V}}}_{\mathrm{\text{O}}}$ as donors have lowest formation energy for all Fermi level at high temperature and low oxygen partial pressure $(T=1500\mathrm{\text{K}}$, $P_{\mathrm{\text{O}}2}=10^{-10}\mathrm{\text{atm}})$. According to our analysis, the ${\mathrm{\text{V}}}_{\mathrm{\text{O}}}$ could produce $n$-type doping in ZnO at these special conditions and change $p$-type ZnO to $n$-type ZnO at condition from low temperature and high oxygen partial pressure to high temperature and low oxygen partial pressure.

The influence of pressure and $\beta$-radiation (1 kGy $\beta$ doses) on the charge transport mechanism, charge trapping effects in porous zeolite surfaces and breakdown voltage $(U_B)$ are discussed in atmospheric microplasmas for the first time. This is due to exposure the zeolite cathode (ZC) to $\beta$-radiation resulting in substantial decreases in the $U_B$, discharge currents and conductivity due to increase in porosity of the material. Results indicated that the enhancement of plasma light intensity and electron emission from the ZC surface with the release of trapped electrons which are captured by the defect centers following $\beta$-irradiation. The porosity of the ZC and radiation defect centers has significant influence on the charge transport of the microstructure and optical properties of the devices manufactured on its base. Thus, we confirm that the ${\mathrm{\text{ZC}}}_{\mathrm{\text{ir}}}$ is a suitable cathode material for plasma light source, field emission displays, energy storage devices and low power gas discharge electronic devices.

${\mathrm{\text{Fe}}}_{81}{\mathrm{\text{Zr}}}_3{\mathrm{\text{Nb}}}_6{\mathrm{\text{B}}}_{10}$ amorphous alloy was prepared by melt-spinning and annealed at various temperatures. The thermal property, microstructure and magnetic property were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The crystallization process of ${\mathrm{\text{Fe}}}_{81}{\mathrm{\text{Zr}}}_3{\mathrm{\text{Nb}}}_6{\mathrm{\text{B}}}_{10}$ alloy is as follow: Amorphous $\to$ residual amorphous $+\alpha$-$\mathrm{\text{Fe}}+\alpha$-$\mathrm{\text{Mn type}}\to \alpha$-$\mathrm{\text{Fe}}$ solid solution. Coercivity $(H_c)$ of ${\mathrm{\text{Fe}}}_{81}{\mathrm{\text{Zr}}}_3{\mathrm{\text{Nb}}}_6{\mathrm{\text{B}}}_{10}$ alloy changes complexly, which abruptly deteriorates at 843 K and then softens with increasing annealing temperature $(T_a)$.

We present a theoretical mechanism for electric field enhancement with SERS of InAs particles of subwavelength apertures under THz excitation. The distribution of electric field confirms that there is a strong enhancement in the InAs particles at THz frequencies. The InAs with a Drude-like behavior in THz range, which is similar to metals at optical frequencies, leads to different SERS when the parameters of these two particles change. The SERS enhancement factor can reach $10^{11}$ under the certain conditions.

${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{25}$ bulk metallic glass (BMG) exhibits good glass forming ability (GFA) and excellent magneto-caloric effect (MCE). In order to further improve the GFA and MCE of the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{25}$ BMG, we attempted to add small amount of Fe as a replacement of Co in the BMG and obtained ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{23}{\mathrm{\text{Fe}}}_2$ glassy rod using a traditional suction casting method. The ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG shows a better GFA and MCE than the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{25}$ BMG. The magneto-caloric behavior of the ${\mathrm{\text{Gd}}}_{55}{\mathrm{\text{Al}}}_{20}{\mathrm{\text{Co}}}_{23}{\mathrm{\text{Fe}}}_2$ BMG was investigated by studying the field dependence of the magnetic entropy change peak and the refrigeration capacity.

In this paper, first-principles calculations based on density functional theory (DFT) have been performed to investigate the adsorption of oxygen and hydrogen on $\mathrm{\text{Pt}}(111)$ and $\mathrm{\text{Pd}}(111)$ surfaces covered by monolayer (ML) of $\mathrm{\text{Pt}}({\mathrm{\text{Pt}}}_{\mathrm{\text{ML}}}/\mathrm{\text{Pd}}(111))$. The results have shown that the oxygen molecule tends to adsorb on fcc site on both surfaces at the coverage of 0.25 ML, which becomes degeneration with hcp site when the coverage increases to 1 ML. For both oxygen and hydrogen, the adsorption on ${\mathrm{\text{Pt}}}_{\mathrm{\text{ML}}}/\mathrm{\text{Pd}}(111)$ surface are stronger than those on $\mathrm{\text{Pt}}(111)$ surface. The adsorption energy difference for oxygen on the two surfaces is $\sim$0.2 eV at the coverage of 1 ML, which increases to $\sim$0.6 eV with the coverage decreasing to 0.25 ML. The similar energy difference was also found for hydrogen adsorption. The density of states analysis have demonstrated the chemical interaction of adsorbed oxygen with both pure $\mathrm{\text{Pt}}(111)$ and ${\mathrm{\text{Pt}}}_{\mathrm{\text{ML}}}/\mathrm{\text{Pd}}(111)$ surfaces with certain shift of $\mathrm{\text{O}}2p$ states to lower level compared to isolated oxygen. For hydrogen adsorption, the hybridization of $\mathrm{\text{H}}1s$ with $\mathrm{\text{Pt}}5d$ states were observed for both surfaces, indicating the covalent bonding component of H–Pt bond.