CONTAMINATION RELEASE TO THE ENVIRONS (1 REPORT)

Daily check of 325 stack filters on 5/9/66 revealed contamination released to the atmosphere within the operating area. Investigation indicated that about 0.4 Ci (mostly Ce-144) had been released as a result of steam jet transfer of some Ce-141-144 from a cask to a storage vault in 325-A. on 5/9/66. A further release of about 0.2 Ci vas indicated by survey of stack filters 5/12/66 following completion ot the transfer. Actions taken include vehicle smears, ground surveys around the 300 area fence line, and smears of the 329 loading dock. Daily check or 325 stack filters on 5-9-66 shoved an increase from about 8000 c/m (GM) Friday afternoon to about 450 mrads/hr (CP) Monday afternoon. Vehicle smears on 4-12 shift 5/9/66, ground surveys around the 300 Area fence line, and smears of the 329 loading dock have not revealed any contamination spread. Inventory in 325A (5/10/66) includes about 3 x 10{sup 6} Ci Ce-141-144 and about 3 x 10{sup 6} Ci Pm-147

Phonon dispersion and electron-phonon coupling in MgB_2 and AlB_2

We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB_2 and the isostructural AlB_2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions \alpha^2F are calculated for both systems. We also report on Raman measurements, which support the theoretical findings. The calculated generalized density-of-states for MgB_2 is in excellent agreement with recent neutron-scattering experiments. The main differences in the calculated phonon spectra and \alpha^2F are related to high frequency in-plane boron vibrations. As compared to AlB_2, they are strongly softened in MgB_2 and exhibit an exceptionally strong coupling to electronic states at the Fermi energy. The total coupling constants are \lambda_{MgB_2}=0.73 and \lambda_{AlB_2}=0.43. Implications for the superconducting transition temperature are briefly discussed.Comment: 10 pages, 4 figures, to appear in Phys. Rev. Let

Spin-orbit driven Peierls transition and possible exotic superconductivity in CsW2_{2}O6_{6}

We study \textit{ab initio} a pyrochlore compound, CsW$_{2}$O$_{6}$, which exhibits a yet unexplained metal-insulator transition. We find that (1) the reported low-$T$ structure is likely inaccurate and the correct structure has a twice larger cell; (2) the insulating phase is not of a Mott or dimer-singlet nature, but a rare example of a 3D Peierls transition, with a simultaneous condensation of three density waves; (3) spin-orbit interaction plays a crucial role, forming well-nested bands. The high-$T$ (HT) phase, if stabilized, could harbor a unique $e_{g}+ie_{g}$ superconducting state that breaks the time reversal symmetry, but is not chiral. This state was predicted in 1999, but never observed. We speculate about possible ways to stabilize the HT phase while keeping the conditions for superconductivity

Lattice dynamics and electron-phonon interaction in (3,3) carbon nanotubes

We present a detailed study of the lattice dynamics and electron-phonon coupling for a (3,3) carbon nanotube which belongs to the class of small diameter based nanotubes which have recently been claimed to be superconducting. We treat the electronic and phononic degrees of freedom completely by modern ab-initio methods without involving approximations beyond the local density approximation. Using density functional perturbation theory we find a mean-field Peierls transition temperature of approx 40K which is an order of magnitude larger than the calculated superconducting transition temperature. Thus in (3,3) tubes the Peierls transition might compete with superconductivity. The Peierls instability is related to the special 2k_F nesting feature of the Fermi surface. Due to the special topology of the (n,n) tubes also a q=0 coupling between the two bands crossing the Fermi energy at k_F is possible which leads to a phonon softening at the Gamma point.Comment: 4 pages, 3 figures; to be published in Phys. Rev. Let