Electronic structure of copper intercalated transition metal dichalcogenides: First-principles calculations

We report first principles calculations, within density functional theory, of copper intercalated titanium diselenides, CuxTiSe2, for values of x ranging from 0 to 0.11. The effect of intercalation on the energy bands and densities of states of the host material is studied in order to better understand the cause of the superconductivity that was recently observed in these structures. We find that charge transfer from the copper atoms to the metal dichalcogenide host layers causes a gradual reduction in the number of holes in the otherwise semi-metallic pristine TiSe2, thus suppressing the charge density wave transition at low temperatures, and a corresponding increase in the density of states at the Fermi level. These effects are probably what drive the superconducting transition in the intercalated systems.Comment: 8 pages, 6 figure

Acoustic reflection from temperature microstructure

This thesis develops a numerical technique to predict the acoustic reflection from an arbitrary sound speed microstructure in the ocean (or a temperature microstructure in the fresh water). This numerical technique is able to reproduce the theoretical formulas for calculating the reflection coefficients of two analytically defined transition layers. The 50 kHz acoustic reflection coefficients from the temperature The 50 kHz acoustic reflection coefficients from the temperature microstructure measured in a fresh-water reservoir was predicted to be less than -90 dB and was found to be much weaker than the observed volume scattering which was due to the biological activities

On The Low-Frequency Vibrational Modes of C60_{60}

The vibrational spectrum of C$_{60}$ is compared to the spectrum of a classical isotropic elastic spherical shell. We show correlations between the low frequency modes of C$_{60}$ and those of the spherical shell. We find the spherical model gives the approximate frequency ordering for the low frequency modes. We estimate a Poisson ratio of $\sigma\approx 0.30$ and a transverse speed of sound of $v_s\approx 1800$ m/s for the equivalent elastic shell. We also find that $\omega({\rm M_1})/\omega({\rm M_0})=\sqrt{3\over 2}$ for the shell modes ${\rm M_0}$ and ${\rm M_1}$, independent of elastic constants. We find that this ratio compares favorably with an experimental value of 1.17.Comment: 11 pages, 3 figures in Postscript, uses REVTEX, to be published in Chem. Phys. Let