Electrides, which accommodate excess of electrons in lattice interstitials as anions, usually exhibit interesting properties and broad applications. Until now, most electrides, especially at high pressures, show semiconducting/insulating character arising from the strong localization of interstitial and orbital electrons. However, modulating their connectivity could turn them into metals and even superconductors. In this work, with the aid of first-principles particle swarm optimization, we have identified a series of pressure-induced Li-rich electrides in the Li-Te system, in which hollow Li n polyhedra accommodate the excess of electrons. With increasing Li content, these electrides undergo an interesting structural evolution. Meanwhile, the connection type of Li n polyhedra experiences transitions from vertex-or edge sharing, to face sharing, leading to a diverse distribution and connectivity of interstitial electrons. All identified electrides exhibit anionic electrons-dominated metallicity. More interestingly, Li 9 Te, with the highest content of Li 6 octahedra, is superconducting with a critical temperature (T c ) of 10.2 K at 75 GPa, which is much higher than typical electrides (e.g., 12CaO • 7Al 2 O 3 , Ca 2 N, and Y 2 C). Its superconductivity mainly originates from the coupling between hybridized electrons (anionic and atomic non-s-state ones) and Te-dominated phonons.

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Beryllium oxides, at ambient pressure, have been extensively studied due to their unique chemical bonds and applications. However, the long-desirable target beryllium peroxide (BeO) has not been reported, thus far. Currently, the application of pressure has become a powerful tool in finding unusual stoichiometric compounds with exotic properties. Here, swarm structural searches in combination with first-principles calculations disclosed that the reaction of BeO and oxygen, at pressures above 89.6 GPa, yields BeO. Interestingly, this reaction pressure is lower than the phase transition pressure (106 GPa) of pure BeO. BeO crystallizes in FeS-type structure, whose remarkable feature is that it contains peroxide group (O) with an O-O distance of 1.40 Å at 100 GPa. Notably, O is maintained in the pressure range of 89.6-300 GPa. The chemical bonding analysis shows that the uniformly distributed ionic Be-O and covalent O-O bonding network plays a key role in determining its structural stability. BeO is a direct band gap nonmetal, and its band gap becomes larger with increase of pressure, which is in sharp contrast with BaO. Moreover, phase diagram of Be-O binary compounds with various BeO (x = 1-3, y = 1-6) compositions at pressures of up to 300 GPa was reliably built. Our results are also important for enriching the understanding of beryllium oxides.

The discovery of two-dimensional (2D) materials with direction-control behavior, wide band gap, and high carrier mobility is highly desirable for the development of advanced optoelectronic devices with photoresponse in the blue and ultraviolet range. Here, we predict an ideal optoelectronic material, a buckled graphene-like PC 6 N, which not only shows a direct wide band gap of 2.56 eV and anisotropic high hole mobility (10 4 cm 2 V −1 s −1 ) but is also transparent to visible light and has a high absorption coefficient (10 5 cm −1 ) in the ultraviolet region. In this way, PC 6 N presents both a wide band gap and high mobility, a long-pursued target in the 2D semiconducting field. Lone electron pairs, originated from N and P atoms, disconnect delocalized π electrons of C 6 rings, making the material a semiconductor. Its anisotropic charge transport can be attributed to the direction-dependent atomic arrangement. PC 6 N shows a high melting point, good dynamical stability, and oxidation resistance to air. These interesting properties make the PC 6 N monolayer a promising candidate for application in novel electronic devices.