Modern Physics Letters B

The Na doping effects on the high temperature thermoelectric properties of ${\mathrm{\text{Bi}}}_{2-x}{\mathrm{\text{Na}}}_x{\mathrm{\text{Sr}}}_2{\mathrm{\text{Co}}}_2{\mathrm{\text{O}}}_y$ ($x$ = 0, 0.05, 0.10, 0.15, 0.20 and 0.30) ceramics were investigated from 343 K to 973 K. When $x\le 0.15$, the electrical resistivity of ${\mathrm{\text{Bi}}}_{2-x}{\mathrm{\text{Na}}}_x{\mathrm{\text{Sr}}}_2{\mathrm{\text{Co}}}_2{\mathrm{\text{O}}}_y$ decreases with increasing Na doping amount due to the hole-doping effect, which exhibits metallic electrical conductivity behavior. While, at the temperature range of 480–830 K, the samples with $x>0.20$ exhibit semiconductor electrical conductivity behavior instead. The Seebeck coefficients are improved by Na doping at lower temperature, but they decrease slightly at higher temperature except for $x=0.2$. Roughly, the thermal conductivity is depressed by the doping defects. As an overall result, the dimensionless figure of merit $(ZT)$ of ${\mathrm{\text{Bi}}}_{1.8}{\mathrm{\text{Na}}}_{0.2}{\mathrm{\text{Sr}}}_2{\mathrm{\text{Co}}}_2{\mathrm{\text{O}}}_y$ reaches the maximum value of 0.3 K at 973 K, which is nearly twice the value of the undoped sample ${\mathrm{\text{LBFS}}}_x$.

Functionalization of ${\mathrm{\text{MoS}}}_2$ monolayer doped by the transition-metal Fe adatom $(\mathrm{\text{Fe}}$–${\mathrm{\text{MoS}}}_2)$ and NO absorption on $\mathrm{\text{Fe}}$–${\mathrm{\text{MoS}}}_2$ has been investigated computationally using first-principles calculations based on the density functional theory. We found that the system of $\mathrm{\text{Fe}}$–${\mathrm{\text{MoS}}}_2$ remains a semiconductor, with spin polarization at the Fermi level. However, for the system with absorption of NO molecule on the surface of $\mathrm{\text{Fe}}$–${\mathrm{\text{MoS}}}_2$ monolayer, its spin polarization is turned over at the Femi level, which provides a promising material for spintronic sensors.

On the basis of the thermal equation-of-state a simple theoretical model is developed to study the pressure dependence of melting temperature. The model is then applied to compute the high pressure melting curve of 10 metals (Cu, Mg, Pb, Al, In, Cd, Zn, Au, Ag and Mn). It is found that the melting temperature is not linear with pressure and the slope $d{T}_m/dP$ of the melting curve decreases continuously with the increase in pressure. The results obtained with the present model are also compared with the previous theoretical and experimental data. A good agreement between theoretical and experimental result supports the validity of the present model.

In this paper, diamond single crystals doped with LiH and boron additives were synthesized in ${\mathrm{\text{Fe}}}_{64}{\mathrm{\text{Ni}}}_{36}$–$\mathrm{\text{C}}$ system under high pressure and high temperature. Under the fixed pressure condition, we found that the synthesis temperature increased slightly after the addition of LiH in the synthesis system. The {100}-orientated surface morphology was investigated by scanning electron microscopy (SEM). The nitrogen concentration in the obtained diamond was analyzed and evaluated using Fourier transmission infrared spectroscopy (FTIR). Furthermore, the electrical properties of Ib-type and boron-doped diamond before and after hydrogenation using Hall effect measurement, which suggested that the conductivity of diamond co-doped with hydrogen and boron was obviously enhanced than that of boron-doped diamond.

We investigate evolution of properties of an extended $s$-wave superconductor, when the order parameter varies from an $s$-wave to a $g$-wave continuously, by using a model order parameter $\Delta (\widehat{k})={\Delta }_0((1-x)+x{sin}^4\theta cos4\varphi )$. The evolution of the gap amplitude, the density of states and the specific heat are mainly focused on. For $x<0.5$, due to the existence of a finite sized gap, the characteristic behaviors more or less follow those of the $s$-wave. Sudden changes in the characteristic behaviors come out for $x\ge 0.5$, due to appearances of nodes. For $x=0.5$, point nodes in the order parameter on the Fermi surface appear, while for $x>0.5$, line nodes appear. Although they are different kinds of nodes which would usually induce different power-law dependencies in superconducting properties, interestingly enough, they give rise to the same characteristic behavior. The detailed structure of the point nodes for $x=0.5$ is investigated, and it is explained why they lead to the same dependence as the line nodes.

The suppression of the pattern complexity of spatiotemporal chaos in Coupled Acousto-optic Bistable Map Lattice system (CABMLs) is investigated. The pattern complexity of spatiotemporal dynamics is exhibited quantitatively by employing the average Kolmogorov–Sinai (KS) entropy density according to the Lyapunov exponents of lattices. By designing a global control method with periodic state feedback, we provide the stability analysis for suppressing spatiotemporal chaos to a stable state. Then, a pattern control strategy using discrete-space state feedback with equal intervals is proposed. Numerical simulations demonstrate that the pattern complexity of spatiotemporal chaos is decreased to a low level by the proposed method. Finally, the dependence of the control effect on the control interval is discussed in detail by considering the control efficiency and control cost and the optimal control interval is obtained.

A proactive quantum secret sharing scheme is proposed, in which the participants can update their shadows periodically. In an updating period, one participant randomly generates the GHZ states and sends the particles to the other participants, and the participants update their shadows according to the measurement performed on the particles. After an updating period, each participant can change his shadow but the secret is changeless. The old shadows will be useless even if they have been stolen by the attacker. The proactive property is very useful to resist the mobile attacker.

The ground state properties of the silicon clathrate ${\mathrm{\text{Si}}}_{46}$ intercalated by alkali metal sodium atoms $({\mathrm{\text{Na}}}_8{\mathrm{\text{Si}}}_{46})$ are investigated by first-principle methods. Birch–Murnaghan equation of state is fitted to two sets of the $E$–$V$ data calculated by density functional theory based on the plane-wave basis set within both the local density approximation (LDA) and the generalized gradient approximation (GGA). Through quasi-harmonic Debye model, some thermodynamic properties comprise the heat capacity, the thermal expansion coefficient, Debye temperature and the Grüneisen parameter for this clathrate compounds ${\mathrm{\text{Na}}}_8{\mathrm{\text{Si}}}_{46}$ are obtained, which agree well with experimental results. Comparing the calculated heat specific in two ways with experimental results, we find that it is more accurate to describe the “rattle” modes of gust Na atoms in the cages as Einstein oscillators. Moreover, the effects of high pressure on these thermodynamic properties are also investigated which will be very helpful for a synthesis of these clathrate compounds in experiments under high pressure and high temperature condition.