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The exploitation of piezoelectric ferromagnetism (PFM) in two-dimensional (2D) materials with large out-of-plane piezoelectric response is motivated not only by technological applications but also scientific interest. In this study, the CrONM monolayer family (N=F, Cl; M=Br, Cl) was investigated using first-principles calculations, revealing that the Janus CrOFBr monolayer exhibits intrinsic ferromagnetic semiconductor behavior along with a significant out-of-plane piezoelectric effect. The calculated out-of-plane piezoelectric strain coefficients d$_{31}$ and d$_{32}$ are up to 1.21 and 0.63 pm/V, respectively. These values are greater than those of the majority of 2D materials. Furthermore, our findings demonstrate that applying tensile strain can enhance the out-of-plane piezoelectric response, leading to a respective 27% and 67% augmentation in the piezoelectric strain coefficients d$_{31}$ and d$_{32}$ compared to the unstrained configurations. This discovery holds great potential for propelling the field of nanoelectronics forward and facilitating the development of multifunctional semiconductor spintronic applications. Finally, by comparing d$_{31}$ and d$_{32}$ of the CrONM monolayer family (N=F, Cl; M=Br, Cl), we find that the magnitudes of d$_{31}$ and d$_{32}$ are correlated with the electronegativity difference between the M and N atoms. These findings provide valuable insights for the design of 2D piezoelectric materials with enhanced vertical piezoelectric responses., Comment: 21 pages, 6 figures

Dislocation slip and deformation twin are widely regarded as two important mechanisms of active competition in the process of plastic deformation. Calculating and comparing the critical resolved shear stress (CRSS) of two deformation modes are the key to discussing the mechanical properties reflected by different mechanisms in crystals. Here, the paper proposes a model to predict the CRSS of discrete twins, resembling thin layers, using the elastic anisotropy theory and a macroscopic energy perspective. In addition, the directionality of deformation twinning is also verified. We investigated twinning in FCC crystals to illustrate the methodology, and predicted the CRSS of twinning under different variables such as temperature and strain rate, both of which were in excellent agreement with experimental and other theory results. It draws the conclusion that we can promote twinning nucleation by applying shear stress along the <112> direction to reduce the interface energy as a resistance term and increase the difference in strain energy for twinning nucleation. This conclusion provides a guiding direction for exploring and accurately predicting the conditions of twinning in FCC crystals in future., Comment: 20 pages, 4 figures

The discovery of superconductivity in CaC6 with a critical temperature (Tc) of 11.5 K reignites much interest in exploring high-temperature superconductivity in graphite intercalation compounds (GICs). Here we identify a GIC NaC4, discovered by ab initio evolutionary structure search, as a superconductor with a computed Tc of 41.2 K at 5 GPa. This value is eight times higher than that of the synthesized GIC NaC2 and possesses the highest Tc among available GICs. The remarkable superconductivity of GIC NaC4 mainly arises from the coupling of {\pi} electrons in graphene with the low-frequency vibrations involving both Na and C atoms. These findings suggest that Na-GICs may hold great promise as high-Tc superconductors., Comment: 4 figures

Located at crystal voids, interstitial anion electrons (IAEs) have diverse topologies, which may be tuned to achieve new properties. Elucidating the role of IAEs in electron-phonon coupling (EPC), and using it to design new electride superconductors, leads to the current prediction of superconducting Li8Au at high pressure. We suggest that the occurence of high-temperature superconductivity in electrides requires high-symmetry structures with hydrogen-like cages, an electron acceptor element to balance charges, and isolated IAEs coupled with medium-frequency vibrations. The uniquely designed Li8Au electride has a NaCl-type (B1) lattice, with atomic Au and cubic Li8 cages as bases. Isolated IAEs are formed at the cage centers, with extra charges taken up by Au. These octahedrally coordinated IAEs have a p-orbital-like attribute and are strongly coupled with atomic vibrations in the Li8 cages. The strong EPC in Li8Au results in a calculated Tc of 73.1 K at 250 GPa, which is the highest Tc reported to date for all the electrides. A slight substitutional Pt doping can enhance the Tc of Li8Au to exceed liquid nitrogen temperature., Comment: 7 Pages, 3 Figures

Two-dimensional (2D) half-metallic materials that have sparked intense interest in advanced spintronic applications are essential to the developing next-generation nanospintronic devices. Here we have adopted a first-principles calculation method to predict the magnetic properties of intrinsic, Se-doped, and biaxial strain tuning Cr$_2$AsP monolayer. The Janus Cr$_2$AsP monolayer is proved to be an intrinsic ferromagnetic (FM) semiconductor with a exchange splitting bandgap of 0.15 eV at the PBE+U level. Concentration-dependent Se doping such as Cr$_2$As$_{1-x}$Se$_x$P (x = 0.25, 0.50, 0.75) can regulate Cr$_2$AsP from FM semiconductor to FM half-metallicity. Specifically, the spin-up channel crosses the Fermi level, while the spin-down channel has a bandgap. More interestingly, the wide half-metallic bandgaps and spin bandgaps make them have important implications for the preparation of spintronic devices. At last, we also explore the effect of biaxial strain from -14% to 10% on the magnetism of the Cr$_2$AsP monolayer. There appears a transition from FM to antiferromagnetic (AFM) at a compressive strain of -10.7%, originating from the competition between the indirect FM superexchange interaction and the direct AFM interaction between the nearest-neighbor Cr atoms. Additionally, when the compressive strain to -2% or the tensile strain to 6%, the semiconducting Cr$_2$AsP becomes a half-metallic material. These charming properties render the Janus Cr$_2$AsP monolayer with great potential for applications in spintronic devices., Comment: 14 pages, 4 figures

Helium (He) is the most inert noble gas at ambient conditions. It adopts a hexagonal close packed structure (P63/mmc) and remains in the insulating phase up to 32 TPa. In contrast, lithium (Li) is one of the most reactive metals at zero pressure, while its cubic high-pressure phase (Fd-3m) is a weak metallic electride above 475 GPa. Strikingly, a stable compound of Li5He2 (R-3m) was formed by mixing Fd-3m Li with P63/mmc He above 700 GPa. The presence of helium promotes the lattice transformation from Fd-3m Li to Pm-3m Li, and tuns the three-dimensional distributed interstitial electrons into the mixture of zero- and two-dimensional anionic electrons. This significantly increases the degree of metallization at the Fermi level, consequently, the coupling of conductive anionic electrons with the Li-dominated vibrations is the key factor to the formation of superconducting electride Li5He2 with a transition temperature up to 26 K, dynamically stable to pressures down to 210 GPa., Comment: 5 pages, 3 figures

Two-dimensional (2D) ferromagnetic materials present promising candidates for spintronic devices, and the half-metallic materials with 100% spin polarization at Fermi energy level are highly desired for many spin-based devices. 2D Janus materials have attracted great attention in recent years due to their excellent properties induced by breaking the symmetry. Here, using the density functional theory, we report that the Janus V2AsP monolayer demonstrates a charming ferromagnetic half-metallic feature. It is dynamically stable in view of the absence of imaginary frequency phonon. The half-metallic gap is about 0.38 eV and the spin splitting of about 1.34eV for the V2AsP monolayer. Interestingly, a tensile strain of 4.9% can induce it to undergo a phase transition from ferromagnetic to anti-ferromagnetic state. Moreover, the Curie temperature (Tc) enhances with the increase of compressive strain. All there appealing properties make the half-metallic Janus V2AsP monolayer a promising material for 2D spintronic applications., Comment: 13pages, 4figures

The exploration of superconductivity dominated by structural units is of great interest in condense matter physics. MgB2, consisting of graphene-like B, becomes a typical representative of traditional superconductors. Phosphorus demonstrates diverse non-planar motifs through sp3 hybridization in allotropes and phosphides. Here, we report that a pressure-stabilized LaP2, isostructural to MgB2, shows superconductivity with a predicted Tc of 22.2 K, which is the highest among already known transition metal phosphides. Besides electron-phonon coupling of graphene-like P, alike the role of B layer in MgB2, La 5d/4f electrons are also responsible for the superconducting transition. Its dynamically stabilized pressure reaches as low as 7 GPa, a desirable feature of pressure-induced superconductors. The distinct P atomic arrangement is attributed to its sp2 hybridization and out-of-plane symmetric distribution of lone pair electrons. Although P is isoelectronic to N and As, we hereby find the different stable stoichiometries, structures, and electronic properties of La phosphides compared with La nitrides/arsenides at high pressure., Comment: 7 pages, 4 figures

Search for new high-temperature superconductors and insight into their superconducting mechanism are of fundamental importance in condensed matter physics. The discovery of near-room temperature superconductivity at more than a million atmospheres ushers in a new era for superconductors. However, the critical task of identifying materials with comparable superconductivity at near or ambient pressure remains. Carbon materials can always lead to intriguing surprises due to their structural diversity and electronic adjustability. Insulating diamond upon doping or external stimuli has achieved superconducting state. Thus, it still has a great opportunity to find superconducting ones with higher transition temperature (Tc). Here, we report an intrinsic superconducting graphite-diamond hybrid through first-principles calculations, whose atomic-resolution structural characteristics have been experimentally determined recently. The predicted Tc is approximated at 39 K at ambient pressure, and strain energizing can further boost Tc to 42 K. The strong electron-phonon coupling associated with the out-of-plane vibration of carbon atoms at the junction plays a dominant role in the superconducting transition. Our work demonstrates the great potential of such carbon materials as high-Tc superconductors, which will definitely attract extensive research., Comment: 11 pages, 3 figures

Novel structural building blocks in compounds could induce interesting physical and chemical properties. Although phosphorus tends to form very different motifs, the existence of lone pair electrons has always prevented the formation of graphenelike structures. Here, the application of first-principles swarm structural calculations has allowed us to predict the stability of pressure-induced hexagonal LaP2H2 containing graphenelike phosphorus, which derives from the trigonal bipyramid configuration of P atoms regulated by symmetric hydrogen bonds. LaP2 in LaP2H2 has the same configuration as MgB2, and P and H atoms form a three-dimensional framework as H3S. Interestingly, LaP2H2 shows a superconductivity dominated by the graphenelike phosphorus layer and its coupling with La atoms. On the other hand, LaP2H2 is not only superconducting at a lower pressure than the H-rich LaPH6, but it also shows a superconducting transition temperature three times higher. Our work provides an example which extends the landscape of conventional superconductors at lower pressures., Comment: 6 pages, 3 figures

The geological conundrum of sulfur excess refers to the finding that predicted amounts of sulfur, in the form of SO2, discharged in volcanic eruptions much exceeds the sulfur available for degassing from the erupted magma. Exploring the source of the excess sulfur has been the subject of considerable interest. Here, from a systematic computational investigation of sulfur-oxygen compounds under pressure, a hitherto unknown S3O4 compound containing a mixture of sulfur oxidation states +II and +IV emerges and is predicted to be stabilized above a pressure of 79 GPa. We predict that S3O4 can be produced via multiple redox reactions involving subducted S-bearing minerals (e.g., sulfates and sulfides) at high pressure conditions relevant to the deep lower mantle, and conversely be decomposed into SO2 and S at shallow depths of Earth. Therefore, S3O4 can be considered as a key intermediate compound to promote the decomposition of sulfates to release SO2, which offers an alternative source of the excess sulfur released during explosive eruptions. These findings provide a possible resolution to the geological paradox of excess sulfur degassing and a viable mechanism for the understanding of S exchange between surface and the lower mantle for the deep sulfur cycle., Comment: 18 pages, 12 figures

Boron-based clathrate materials, typically with three-dimensional networks of B atoms, have tunable properties through substitution of guest atoms, but the tuning of B cages themselves has not yet been developed. By combining crystal structural search with the laser-heated diamond anvil cell technique, we successfully synthesized a new B-based clathrate boride, LaB8, at ~108 GPa and ~2100 K. The novel structure has a B-richest cage, with 26 B atoms encapsulating a single La atom. LaB8 demonstrates phonon-mediated superconductivity with an estimated transition temperature of 14 K at ambient pressure, mainly originating from electron-phonon coupling of B cage. This work creates a prototype platform for subsequent investigation on tunable electronic properties through the choice of captured atoms.

Selective attention plays an essential role in information acquisition and utilization from the environment. In the past 50 years, research on selective attention has been a central topic in cognitive science. Compared with unimodal studies, crossmodal studies are more complex but necessary to solve real-world challenges in both human experiments and computational modeling. Although an increasing number of findings on crossmodal selective attention have shed light on humans' behavioral patterns and neural underpinnings, a much better understanding is still necessary to yield the same benefit for computational intelligent agents. This article reviews studies of selective attention in unimodal visual and auditory and crossmodal audiovisual setups from the multidisciplinary perspectives of psychology and cognitive neuroscience, and evaluates different ways to simulate analogous mechanisms in computational models and robotics. We discuss the gaps between these fields in this interdisciplinary review and provide insights about how to use psychological findings and theories in artificial intelligence from different perspectives., Comment: 29pages, 5 figures, 1 table, journal article

Electrides are unique compounds where most of the electrons reside at interstitial regions of the crystal behaving as anions, which strongly determines its physical properties. Interestingly, the magnitude and distribution of interstitial electrons can be effectively modified either by modulating its chemical composition or external conditions (e.g. pressure). Most of the electrides under high pressure are non-metallic, and superconducting electrides are very rare. In this work we report that a pressure-induced stable Li6P electride becomes superconductor with a Tc of 39.3 K, which is the highest among already known electrides. The interstitial electrons in Li6P, with dumbbell-like connected electride states, play a dominant role in the superconducting transition. Other Li-rich phosphides, Li5P and Li8P, are also predicted to be superconducting electrides, but with a lower Tc. Superconductivity in all these compounds can be attributed to a combination of a weak electronegativity of P with a strong electropositivity of Li, and opens up the interest to explore high-temperature superconductivity in similar binary compounds.

Observation of high-temperature superconductivity in sulfur hydrides at megabar pressures has generated an irresistible wave on searching for new superconductors in other compressed hydrogen-rich compounds. An immediate effort is towards exploration of the relevant candidate of tellurium hydrides, where tellurium is isoelectronic to sulfur but it has a heavier atomic mass and much weaker electronegativity. The hitherto unknown phase diagram of tellurium hydrides at high pressures was investigated by a first-principles swarm structure search. Four energetically stable and metallic stoichiometries of H4Te, H5Te2, HTe and HTe3 were uncovered above 140 GPa, showing a distinct potential energy map of tellurium hydrides from those in sulfur and selenium hydrides. The two hydrogen-rich H4Te and H5Te2 species adopt ionic structures containing exotic quasi-molecular H2 and linear H3 units, respectively. Strong electron-phonon couplings associated with the intermediate-frequency H-derived wagging and bending modes make them good superconductors with high Tc in the range of 46-104 K., Comment: 6 pages, 4 figures plus Supplemental materials. arXiv admin note: text overlap with arXiv:1502.02607

Recent discovery of high-temperature superconductivity (Tc = 190 K) in sulfur hydrides at megabar pressures breaks the traditional belief on the Tc limit of 40 K for conventional superconductors, and open up the doors in searching new high-temperature superconductors in compounds made up of light elements. Selenium is a sister and isoelectronic element of sulfur, with a larger atomic core and a weaker electronegativity. Whether selenium hydrides share similar high-temperature superconductivity remains elusive, but it is a subject of considerable interest. First-principles swarm structure predictions are performed in an effort to seek for energetically stable and metallic selenium hydrides at high pressures. We find the phase diagram of selenium hydrides is rather different from its sulfur analogy, which is indicates by the emergence of new phases and the change of relative stabilities. Three stable and metallic species with stoichiometries of HSe2, HSe and H3Se are identified above ~120 GPa and they all exhibit superconductive behaviors, of which the hydrogen-rich HSe and H3Se phases show high Tc in the range of 40-110 K. Our simulations established the high-temperature superconductive nature of selenium hydrides and provided useful route for experimental verification., Comment: 16 pages, 4 figures plus Supplemental materials