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The experimental discovery of superconductivity was reported in Sm-doped chrysene with Tc ~ 5 K, which provides vital material for exploring unique superconducting mechanism of rare-earth metal doped polycyclic aromatic hydrocarbons. Here the crystal, electronic structures and magnetic characteristics of Sm-doped chrysene have been investigated by the first-principles calculation using the generalized gradient approximation (GGA) plus U method, also including van der Waals correction. We find that Sm-doped chrysene with C2/c space group is the most stable where doped Sm atoms stay on the relative middle of chrysene molecules. This material is stabilized at antiferromagnetic ground-state with the metallic feature. The calculated spin magnetic moment of Sm atom indicates that there are two electrons transferring from Sm to chrysene molecule. Within the framework of GGA+U, the C-2p electronic states mainly contribute to the Fermi surface. Electronic correlation effects are significant to understand the superconductivity in Sm-doped chrysene. [ABSTRACT FROM AUTHOR]

Based on the density functional theory plus the effective Coulomb repulsion U, we have investigated the crystal structure, electronic properties and magnetic characteristics in Sm-doped phenanthrene, recently characterized as a superconductor with Tc ~ 5 - 6 Kelvin. Calculated total energies of different magnetic states indicate that Sm-doped phenanthrene is stable at the ferromagnetic ground-state. Considered the strong electronic correlations effect due to the intercalation of Sm-4f electrons, we found that the Sm-4f contributes to the Fermi surface together with C-2p, which is different from K-doped phenanthrene. Compared with alkali-metaldoped phenanthrene, Sm atom has larger local magnetic moment, which suppresses the superconductivity in conventional superconductors. Our results indicate that the electron-electron correlations play an important role in superconductivity of Sm-doped phenanthrene. [ABSTRACT FROM AUTHOR]

We explore a type piezoelectric material 0.9525(K0.5Na0.5NbO3)-0.0475LiTaO3 (KNN-LTS) which can be used to fabricate nanogenerator with high output voltage and current due to its high piezoelectric constant (d 33). Because of its unique structure mixed with multi-wall carbon nanotube and polydimethylsiloxane, the output voltage is up to 53 V and the output current is up to 15 uA (current density of 12.5 uA/cm²) respectively. The value of the output voltage and output current represent the highest level in the piezoelectric field reported to date. The KNN-LTS nanopowder-based nanogenerator can also be used as a sensitive motion detection sensor. [ABSTRACT FROM AUTHOR]