Graphyne sheet exhibits promising potential for nanoscale desalination to achieve both high water permeability and salt rejection rate. Extensive molecular dynamics simulations on pore-size effects suggest that γ-graphyne-4, with 4 acetylene bonds between two adjacent phenyl rings, has the best performance with 100% salt rejection and an unprecedented water permeability, to our knowledge, of ~13 L/cm2/day/MPa, 3 orders of magnitude higher than prevailing commercial membranes based on reverse osmosis, and ~10 times higher than the state-of-the-art nanoporous graphene. Strikingly, water permeability across graphyne exhibits unexpected nonlinear dependence on the pore size. This counter-intuitive behavior is attributed to the quantized nature of water flow at the nanoscale, which has wide implications in controlling nanoscale water transport and designing highly effective membranes.

Resolving the atomic structure of the surface of ice particles within clouds, over the temperature range encountered in the atmosphere and relevant to understanding heterogeneous catalysis on ice, remains an experimental challenge. By using first-principles calculations, we show that the surface of crystalline ice exhibits a remarkable variance in vacancy formation energies, akin to an amorphous material. We find vacancy formation energies as low as similar to 0.1-0.2 eV, which leads to a higher than expected vacancy concentration. Because a vacancy's reactivity correlates with its formation energy, ice particles may be more reactive than previously thought. We also show that vacancies significantly reduce the formation energy of neighbouring vacancies, thus facilitating pitting and contributing to pre-melting and quasi-liquid layer formation. These surface properties arise from proton disorder and the relaxation of geometric constraints, which suggests that other frustrated materials may possess unusual surface characteristics. 2 Despite ice being a ubiquitous and well-studied substance, it is surprising that some basic questions about its properties and structure are still debated. For example, Faraday contentiously proposed that the surface of hexagonal ice (Ih) was liquid-like to explain a

A microscopic mechanism for the unipolar resistive switching phenomenon in nickel oxides is proposed based on the thermal decomposition of oxygen ions from oxygen-rich clusters and their recombination with electron-depleted vacancies induced by local electric field in conductive filaments. The proposed physical feature is confirmed by x-ray photoelectron spectroscopy, transmission electron microscopy and electrical measurements in the as-deposited NiO x samples. The deduced formulae under reasonable approximations directly demonstrate the relationships of switching parameters that were widely observed and questioned in different material systems, indicating the universal validity of the proposed mechanism.

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It is revealed from first-principles calculations that polarization-induced asymmetric distribution of oxygen vacancies plays an important role in the insulating behavior at p-type LaAlO 3 / SrTiO 3 interface. The formation energy of the oxygen vacancy ͑V O ͒ is much smaller than that at the surface of the LaAlO 3 overlayer, causing all the carriers to be compensated by the spontaneously formed V O 's at the interface. In contrast, at an n-type interface, the formation energy of V O is much higher than that at the surface, and the V O 's formed at the surface enhance the carrier density at the interface. This explains the puzzling behavior of why the p-type interface is always insulating but the n-type interface can be conducting.