We perform first-principles calculations of mechanical and electronic properties of silicene under strains. The in-plane stiffness of silicene is much smaller than that of graphene. The yielding strain of silicene under uniform expansion in the ideal conditions is about 20%. The homogeneous strain can introduce a semimetal-metal transition. The semimetal state of silicene, in which the Dirac cone locates at the Fermi level, can only persist up to tensile strain of 7% with nearly invariant Fermi velocity. For larger strains, silicene changes into a conventional metal. The work function is found to change significantly under biaxial strain. Our calculations show that strain tuning is important for applications of silicene in nanoelectronics

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A-and B-site substituted double-perovskite Sr 2 CaMoO 6 by Eu 3+ have been synthesized using solid-state reactions and characterized by X-ray diffraction, Raman spectroscopy, and photoluminescence measurement. Raman spectra are used to identify the Aand B-site substitutions, because specific Raman peaks corresponding to different ions motion are sensitive to each situation. Raman data reveal that both the A-and B-site substituted solid solutions are formed. The photoluminescence intensity of the B-site substituted Sr 2 CaMoO 6 is evidently higher than that of the A-site substituted phosphor. The WO 6 group introduced into Sr 2 CaMoO 6 :Eu 3+ ,Li + acts as an energy obstacle to prevent energy transfer among MoO 6 groups, leading to more energy being trapped by Eu 3+ , and a higher photoluminescence intensity is obtained. The phosphor with optimized composition Sr 2 Ca 0.80 Li 0.10 Eu 0.10 Mo 0.10 W 0.90 O 6 shows a better luminescence intensity than the commercial phosphor Y 2 O 2 S:Eu under 395 nm excitations.