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.

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MgTiO 3 ceramic sample was synthesized and its Raman spectra were recorded. The Raman-active vibrational modes of MgTiO3 were calculated using first-principle calculations (density functional theory). Based on experimental data and calculation results, the Raman peaks were assigned as 225 cm−1 (Ag), 306 cm−1 (Ag), 398 cm−1 (Ag), 500 cm−1 (Ag), 715 cm−1 (Ag) and 281 cm−1 (Eg), 328 cm−1 (Eg), 353 cm−1 (Eg), 486 cm−1 (Eg), 641 cm−1 (Eg). The assignment was supported by the polarized Raman spectrum. Meanwhile, the symmetry coordinates of MgTiO3 primitive cell were analyzed and employed to expand the Raman-active modes.

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The samples of complex perovskite Ba(Mg1/3Ta2/3)O3 (BMT) were synthesized at various sintering temperatures and the X‐ray diffraction (XRD) patterns and Raman spectra of the samples were collected. Both the structure refinements using the XRD data and the Raman spectra show that the samples sintered above 1500°C with high pellet relative density (>95%) take almost‐perfect B‐site‐ordered structure; while the samples sintered below 1400°C with low pellet relative density (<70%) take the more disordered structure at B‐sites. The vibrational modes of 1:2 ordered BMT were obtained and illustrated by using first‐principle calculations. With the assistance of the calculation results, Raman peaks of BMT were assigned as A1g(1) (107 cm−1), A1g(2) (212 cm−1), A1g(3) (433 cm−1), A1g(4) (798 cm−1), and Eg(1) (104 cm−1), Eg(2) (160 cm−1), Eg(3) (264 cm−1), Eg(4) (386 cm−1), Eg(5) (576 cm−1). The highly ordered BMT sample at B‐site shows longer phonon lifetime and weaker coupling among phonons than the disordered BMT, which probably are the intrinsic reasons for the highly ordered BMT sample to have the low dielectric loss.