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Traditional MXenes with intriguing mechanical and electronic properties, together with the fertilities of elemental compositions and chemical decorations have aroused much attentions. However, the semiconducting traits with direc band gap are extremetely rare among reported MXenes. Thus, broadening the family of MXene beyond carbides and nitrides with unique behaviors is still an extraordinary and fascinating field.

The weak interlayer Van Der Waals material \{beta}-Bi2Pd has recently been established as a strong topological superconductor candidate with unconventional spin-triplet pairing and Majorana zero modes at vortices. In this letter, we study the topological characters and the superconducting pairing, which are still obscure in monolayer \{beta}-Bi2Pd, in light of our effective theoretical model. We find that the non-Rashba spin-orbital coupling plays a critical role in realizing and tuning various novel topological natures. In particular, the spin-triplet p-wave superconducting pairing with Majorana zero mode is revealed in monolayer \{beta}-Bi2Pd. Our studies deepen the understanding of topology and superconductivity in monolayer \{beta}-Bi2Pd and indicate it is a promising platform for achieving low-dimentional topological superconductivity., Comment: 5 pages, 4 figures

Topological superconductors, characterized by topologically nontrivial states residing in a superconducting gap, are a recently discovered class of materials having Majorana Fermions. The interplay of superconductivity and topological states give rise to opportunities for achieving such topological superconductors in condensed matter systems. Up to now, several single-material topological superconductors in this form have been theoretically predicted and experimentally confirmed. Here, using the first-principles calculations, we study the superconducting single-layer $��$-Bi$_{2}$Pd. The electronic density of states near Fermi level of this monolayer are dominated by the Bi-p and Pd-d orbitals, forming a two-band Fermi surface with multi-class sheets. The presence of soft phonon bands, in cooperation with the electron susceptibility, account for electron-phonon superconductivity of single-layer $��$-Bi$_{2}$Pd. With the centrosymmetric structure, single-layer $��$-Bi$_{2}$Pd possesses a continuous gap over the whole Brillouin zone and topological Dirac-like states at its one-dimensional boundary. The present findings would lead to the expectation of one-dimensional topological superconductivity and Majorana bound states in monolayer candidate of $��$-Bi$_{2}$Pd with intrinsic full-gap superconductivity., 7 figures

Low thermal conductivity is favorable for preserving the temperature gradient between the two ends of a thermoelectric material in order to ensure continuous electron current generation. In high-performance thermoelectric materials, there are two main low thermal conductivity mechanisms: the phonon anharmonic in PbTe and SnSe and phonon scattering resulting from the dynamic disorder in AgCrSe2 and CuCrSe2, which have been successfully revealed by inelastic neutron scattering. Using neutron scattering and ab initio calculations, we report here a mechanism of static local structure distortion combined with phonon-anharmonic-induced ultralow lattice thermal conductivity in ��-MgAgSb. Since the transverse acoustic phonons are almost fully scattered by the compound's intrinsic distorted rocksalt sublattice, the heat is mainly transported by the longitudinal acoustic phonons. The ultralow thermal conductivity in ��-MgAgSb is attributed to its atomic dynamics being altered by the structure distortion, which presents a possible microscopic route to enhance the performance of similar thermoelectric materials., 43 pages, 5 figures

Two-dimensional (2D) boron has been predicted to show superconductivity. However, intrinsic 2D carbon and phosphorus have not been reported to be superconductors, which, inspires us to seek superconductivity in their mixture. Here we perform first-principles calculations of the electronic structure, phonon dispersion, and electron-phonon coupling of the metallic phosphorus carbide monolayer, the $��_{0}$-PC. Results show that it is an intrinsic phonon-mediated superconductor, with estimated superconducting temperature $T_{c}$ to be $\sim$13 K. The main contribution to the electron-phonon coupling is from the out-of-plane vibrations of phosphorus. A Kohn anomaly on the first acoustic branch is observed. The superconducting related physical quantities is found tunable by applying strain or carrier doping., 6 pages, 5 figures

The deposition and consolidation behaviour of cohesive sediment is studied with a newly developed integrated settlement column system. This system, which includes graduate (glass) and settlement column (PMMA), has been proved an effective way to study the settlement of sediment suspension with 20∼300 g/L initial concentration. Cohesive sediment deposition and consolidation behaviours are as follows: cohesive sediment settlement can be divided into different stages as the initial free settlement and the consolidation settlement with different sediment interface rate. Cohesive sediment settlement influence factors are mainly the initial concentration and the settlement height, from which, settlement column size effect is determined by three factors as the wall effect, convection effect as well as the flocculation effect. During the final weight consolidation stage, deposited sediment consolidation settlement develops much faster than the excessive pore-pressure dissipation, and the fitted nonlinear consolid...

The recent discovery of topologically protected surface states in the noncentrosymmetric $��$-BiPd and the centrosymmetric $��$-Bi$_{2}$Pd has renewed the interest in the Bi-Pd family of superconductors. Here, we employ first-principles calculations to investigate the structure, electronic, and topological features of $��$-Bi$_{2}$Pd, in bulk and in thin films of various thicknesses. We find that the Van der Waals dispersion corrections are important for reproducing the experimental structural parameters, while the spin-orbit interaction is critical for properly describing the appearance of topological electronic states. By increasing the thickness of the slab, the Dirac-cone surface states and the Rashba-type surface states gradually emerge at 9 and 11 triple-layers., 8 pages, 6 figures

Silt solidification is an important method of silt disposal,and it’s proved to be quick effectiveness and time saving and large in capacity.In recent years,the industrial pollution has made the silt in the lake or the sea rich in harmful elements,such as heavy metal and organic matter,etc,which may strongly influence the solidification effect of silt and trigger secondary pollution.The author proposed a kind of choice,which could effectly decrease harmful elements leaching,based on engineering application.The performances of solidification with different ratio of cement and zeolite,such as unconfined compressive strength,compression coefficient,heavy metal fractions,heavy metal short-term stability and long-term stability are systematicly studied.The article confirmed that the addition of the cement and the zeolite increase the strength of the soil and effectly enhance its deformation resistant capability,Further more,they significantly decrease the activity of harmful elements and greatly reduce the threat to the environment,which finds an effective solution to the environment problem.

The electronic structure and thermodynamical properties of uranium trihydrides ($\alpha$-UH$_{3}$ and $\beta$-UH$_{3}$) have been studied using first-principles density functional theory. We find that inclusion of strong electronic correlation is crucial in successfully depicting the electronic structure and thermodynamic phase stability of uranium hydrides. After turning on the Hubbard parameter, the uranium 5f states are divided into well-resolved multiplets and their metallicity is weakened by downward shift in energy, which prominently changes the hydrogen bond and its vibration frequencies in the system. Without Coulomb repulsion, the experimentally observed $\alpha\mathtt{\rightarrow}\beta$ phase transition cannot be reproduced, whereas, by inclusion of the on-site correlation, we successfully predict a transition temperature value of about 332 K, which is close to the experimental result., Comment: 4 pages, 4 figures

Plutonium dioxide is of high technological importance in nuclear fuel cycle and is particularly crucial in long-term storage of Pu-based radioactive waste. Using first-principles density-functional theory, in this paper we systematically study the structural, electronic, mechanical, thermodynamic properties, and pressure induced structural transition of PuO$_{2}$. To properly describe the strong correlation in the Pu $5f$ electrons, the local density approximation$+U$ and the generalized gradient approximation$+U$ theoretical formalisms have been employed. We optimize the $U$ parameter in calculating the total energy, lattice parameters, and bulk modulus at the nonmagnetic, ferromagnetic, and antiferromagnetic configurations for both ground state fluorite structure and high pressure cotunnite structure. The best agreement with experiments is obtained by tuning the effective Hubbard parameter $U$ at around 4 eV within the LDA$+U$ approach. After carefully testing the validity of the ground state, we further investigate the bonding nature, elastic constants, various moduli, Debye temperature, hardness, ideal tensile strength, and phonon dispersion for fluorite PuO$_{2}$. Some thermodynamic properties, e.g., the Gibbs free energy, volume thermal expansion, and specific heat, are also calculated. As for cotunnite phase, besides the elastic constants, various moduli, and Debye temperature at 0 GPa, we have further presented our calculated electronic, structural, and magnetic properties for PuO$_{2}$ under pressure up to 280 GPa. A metallic transition at around 133 GPa and an isostructural transition in pressure range of 75-133 GPa are predicted., Comment: 14 PRB pages, 15 figures

The elasticity, dynamic properties, and superconductivity of $\alpha$, $\omega$, and $\beta$ Zr are investigated by using first-principles methods. Our calculated elastic constants, elastic moduli, and Debye temperatures of $\alpha$ and $\omega$ phases are in excellent agreement with experiments. Electron-phonon coupling constant $\lambda$ and electronic density of states at the Fermi level $N$(\emph{E}$_{\rm{F}}$) are found to increase with pressure for these two hexagonal structures. For cubic $\beta$ phase, the critical pressure for mechanical stability is predicted to be 3.13 GPa and at \emph{P}=4 GPa the low elastic modulus ($E$=31.97 GPa) can be obtained. Besides, the critical pressure for dynamic stability of $\beta$ phase is achieved by phonon dispersion calculations to be $\mathtt{\sim}$26 GPa. Over this pressure, $\lambda$ and $N$(\emph{E}$_{\rm{F}}$) of $\beta$ phase decrease upon further compression. Our calculations show that the large value of superconducting transition temperature $\emph{T}_{\rm{c}}$ at 30 GPa for $\beta$ Zr is mainly due to the TA1 soft mode. Under further compression, the soft vibrational mode will gradually fade away., Comment: 15 pages, 5 figures