Smooth Flow in Diamond: Atomistic Ductility and Electronic Conductivity

Diamond is the quintessential superhard material widely known for its stiff and brittle nature and large electronic band gap. In stark contrast to these established benchmarks, our first-principles studies unveil surprising intrinsic structural ductility and electronic conductivity in diamond under coexisting large shear and compressive strains. These complex loading conditions impede brittle fracture modes and promote atomistic ductility, triggering rare smooth plastic flow in the normally rigid diamond crystal. This extraordinary structural change induces a concomitant band gap closure, enabling smooth charge flow in deformation created conducting channels. These startling soft-and-conducting modes reveal unprecedented fundamental characteristics of diamond, with profound implications for elucidating and predicting diamond’s anomalous behaviors at extreme conditions

First-principles Study of High-Pressure Phase Stability and Superconductivity of Bi4I4

Bismuth iodide Bi4I4 exhibits intricate crystal structures and topological insulating states that are highly susceptible to influence by environments, making its physical properties highly tunable by external conditions. In this work, we study the evolution of structural and electronic properties of Bi4I4 at high pressure using an advanced structure search method in conjunction with first-principles calculations. Our results indicate that the most stable ambient-pressure monoclinic α−Bi4I4 phase in C2/m symmetry transforms to a trigonal P31c structure (ɛ−Bi4I4) at 8.4 GPa, then to a tetragonal P4/mmm structure (ζ−Bi4I4) above 16.6 GPa. In contrast to the semiconducting nature of ambient-pressure Bi4I4, the two high-pressure phases are metallic, in agreement with reported electrical measurements. The ɛ−Bi4I4 phase exhibits distinct ionic states of Iδ− and (Bi4I3)δ + (δ=0.4123 e), driven by a pressure-induced volume reduction. We show that both ɛ- and ζ−Bi4I4 are superconductors, and the emergence of pressure-induced superconductivity might be intimately linked to the underlying structural phase transitions

Chemical and Electrochemical Studies of Cl\u3csub\u3e2\u3c/sub\u3eFeS\u3csub\u3e2\u3c/sub\u3eMS\u3csub\u3e2\u3c/sub\u3eFeCl\u3csub\u3e2\u3c/sub\u3e\u3csup\u3e\u3cem\u3en\u3c/em\u3e-\u3c/sup\u3e Clusters [M = Mo (n = \u3cem\u3e2\u3c/em\u3e), W (\u3cem\u3en\u3c/em\u3e = 2), V (\u3cem\u3en\u3c/em\u3e = 3)]

The electrochemistry and spectroelectrochemistry of [Cl2FeS2MS2FeCl2]n- clusters (where n = 2 for M = Mo and W and n = 3 for M = V; Ia, Ib, and Ic, respectively) and the dimetal complex [Cl2FeS2MoS2]2- (IIIa) were examined in order to characterize the structures and properties of the one-electron-reduced complexes. A stable reduction product for Ia was observed spectroelectrochemically at −1.05 V, which could be oxidized back to the starting complex. Reduction at more negative potentials caused complete bleaching of the spectrum, and the starting complex could not be obtained by reoxidation. Similar behavior was observed for the tungsten complex, Ib, but the dimetal complex [Cl2FeS2WS2]2- was formed upon reoxidation. Chemical and electrochemical reduction of Ia and Ib both led to the same products (IIa and IIb), but by different mechanisms. Borohydride reduction of Ia and Ib led to the initial formation of the dimetal complex, while the electrochemical reduction of Ia proceeded by way of the formation of [Cl2FeS2MoS2FeCl2]3-. Spectral changes were observed in the reduction of Ic, but they were not reversible. Resonance Raman spectroscopy of the reduced complexes was carried out in order to characterize the reduction product. Two polarized bands in the sulfur bridging region were observed in the resonance Raman spectra of electrochemically and chemically generated IIa and IIb. The relative intensities of these bands were dependent upon the excitation frequency. Reduction of Ic led to the loss of all resonance Raman bands. Reduction of IIIa gave rise to a complex (IVa) that was spectrally quite similar to IIa. These results, along with the previously reported result that the reduction complex was diamagnetic, indicate that the complex IIa is a dimeric species. The most likely structure consistent with these data is a Mo2Fe2S4 cubane structure

How western multinational companies (MNCs) attract post-90s knowledge workers in China

After 2010, China’s GDP overtakes Japan and becomes the world’s second-largest economy, which leads more and more western multinational companies (MNCs) to enter and expand their business in China. Due to differences in culture and social environment, western multinational companies face many challenges when they recruit talents in China. The Chinese government encourages factories to transform from low-level manufacturing to high-tech intelligent manufacturing, requiring a large number of knowledgeable workers to contribute. Therefore, western multinational companies (MNCs) need to formulate a set of recruitment strategies to attract Chinese post-90s knowledge workers. This dissertation uses questionnaire to investigate the factors that Chinese and western post-90s knowledge workers value differently when they choose western multinational companies (MNCs), recruitment channels preferred by Chinese post-90s knowledge workers and Chinese post-90s knowledge workers' job satisfaction with western multinational companies (MNCs). After investigation, we found a set of effective recruitment strategy. Firstly, whether Western or Chinese post-90s knowledge workers value every recruiting factor. Secondly, western multinational companies (MNCs) could simultaneously use multiple recruiting channels to enhance recruiting success rates in China. Thirdly, western multinational companies (MNCs) need to improve these motivators and hygiene factors with professional knowledge to enhance job satisfaction

Rare Helium-Bearing Compound FeO2He Stabilized at Deep-Earth Conditions

There is compelling geochemical evidence for primordial helium trapped in Earth’s lower mantle, but the origin and nature of the helium source remain elusive due to scarce knowledge on viable helium-bearing compounds that are extremely rare. Here we explore materials physics underlying this prominent challenge. Our structure searches in conjunction with first-principles energetic and thermodynamic calculations uncover a remarkable helium-bearing compound FeO2He at high pressure-temperature conditions relevant to the core-mantle boundary. Calculated sound velocities consistent with seismic data validate FeO2He as a feasible constituent in ultralow velocity zones at the lowermost mantle. These mutually corroborating findings establish the first and hitherto only helium-bearing compound viable at pertinent geophysical conditions, thus providing vital physics mechanisms and materials insights for elucidating the enigmatic helium reservoir in deep Earth

Sensitivity Analysis for Coupled Structural-Acoustic System with Absorbing Material Using FEM/BEM

Since the acoustic impedance in water cannot be neglected with respect to the mechanical impedance, the acoustic radiation caused by the vibration of structures in the compressible fluid would react to the structure. Therefore, the fluid-structure interaction needs to be considered. The finite element method is used for structure vibration analysis and the boundary element method for acoustic analysis. Sound absorption materials are used to reduce the scattering sound field in the reference region. The sensitivity analysis of a fully coupled structural-acoustic system is proposed. Numerical tests verify the correctness of the proposed algorithm

Computational Discovery and Characterization of New B2O Phases

We present computational discoveries of new structural phases of B2O compound exhibiting novel bonding networks and electronic states at ambient and elevated pressures. Our advanced crystal structure searches in conjunction with density functional theory calculations have identified an orthorhombic phase of B2O that is energetically stable at ambient pressure and contains an intriguing bonding network of icosahedral B12 clusters bridged by oxygen atoms. As pressure increases above 1.9 GPa, a structural transformation takes the orthorhombic B2O into a pseudo- layered trigonal phase. We have performed extensive studies to investigate the evolution of chemical bonds and electronic states associated with the B12 icosahedral unit in the orthorhombic phase and the covalent B-O bonds in the trigonal phase. We also have examined the nature of the charge carriers and their coupling to the lattice vibrations in the newly identified B2O crystals. Interestingly, our results indicate that both B2O phases become superconducting at low temperatures, with transition temperatures of 6.4 K and 5.9 K, respectively, in the ambient and high-pressure phase. The present findings establish new B2O phases and characterize their structural and electronic properties, which offer insights and guidance for exploration toward further fundamental understanding and potential synthesis and application