Pressure-dependent first-order phase transition, mechanical, elastic, and thermodynamical properties of cubic zinc blende to rock-salt structures in 3C silicon carbide (SiC) are presented. An effective interatomic interaction potential for SiC is formulated. The potential for SiC incorporates long-range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second-neighbour ions, van der Waals interactions and zero point energy effects. The developed potential including many body non-central forces validates the Cauchy discrepancy successfully to explain the high-pressure structural transition, and associated volume collapse. The 3C SiC ceramics lattice infers mechanical stiffening, thermal softening, and ductile (brittle) nature from the pressure (temperature) dependent elastic constants behaviour. To our knowledge, these are the first quantitative theoretical predictions of the pressure and temperature dependence of mechanical and thermodynamical properties explicitly the mechanical stiffening, thermally softening, and brittle/ductile nature of 3C SiC and still awaits experimental confirmations.

We study the interaction of electromagnetic field with two of the most tunable nanostructure geometries for nanoplasmonics including the magneto-optical nanoshell structure and the spheroidal geometry. We investigate the effect of combining both geometry and magneto-optical properties within the same nanostructure on the field enhancement factor and optical bistability behaviors. Since the coupling between the inner and outer surface plasmons of the nanoshell is stronger for the elongated spheroidal geometry as compared to that for the spherical case, field enhancement in ellipsoid nanoparticles is much more saleintiant. Moreover, the plasmonic field enhancement is four orders of magnitude larger for the spheroidal nanoshells as compared to spherical nanoshells. In addition to the appearance of optical bistability in this system, it is found that the threshold and window of bistability are strongly dependent on magneto-optical properties and geometry of the core-shell nanoparticle.

The temperature variation of phonon drag thermoelectric power [Formula: see text] is computed within the relaxation time approximation for high temperature MgB2 superconductors. The phonon drag thermoelectric power ([Formula: see text] in normal state of MgB2 superconductors dominates and is an artifact of strong phonon-impurity and phonon scattering mechanism. The carrier diffusive thermoelectric power is explored when heat transfer is limited by the scattering of phonons from defects, grain boundaries, phonons and charge carriers. The carrier diffusion contribution to the thermoelectric power ([Formula: see text] is analyzed keeping in mind the inherent two energy gaps. The conductivity within the relaxation time approximation for [Formula: see text] and [Formula: see text] band carriers has been taken into account ignoring a possible energy dependence of the scattering rates. Such an estimate sets an upperbound on [Formula: see text] and is about 50% of total heat transfer at room temperature. Both these channels for heat transfer are added and [Formula: see text] starts departing from linear temperature dependence at about 150[Formula: see text]K, before increasing at higher temperatures weakly. It is shown that the behavior of the [Formula: see text] is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions. The numerical analysis of thermoelectric power in the metallic phase of MgB2 shows similar results as those revealed from experiments. The anomalies reported experimentally are well accounted in terms of the scattering mechanism by phonon drag and carrier scattering with impurities.

The thermoelectric power (S) of K3C60 fullerides is theoretically analyzed. Mott expression within parabolic band approximation is used to reveal the electron diffusive thermoelectric power (Sc diff ) following Fermi energy as electron parameter, Sc diff show linear temperature dependence. S infers a change in slope above transition temperature and become almost linear above 70 K. The phonon drag thermoelectric power (S ph drag ) is computed within relaxation time approximation when thermoelectric power is limited by scattering of phonons from defects, grain boundaries, phonons and electrons as carriers. The S ph drag of K3C60 is anomalous and it is an artifact of strong phonon-electron and phonon scattering mechanism. The thermoelectric power within relaxation time approximation has been taken into account ignoring a possible energy dependence of the scattering rates. Behaviour of S(T) is determined by competition among the several operating scattering mechanisms for the heat carriers and a balance between carrier diffusion and phonon drag contributions.

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