Steven S. Trail

New cerium nitride chlorides : Ce6Cl12N2 and CeNCl

Abstract The compound CeNCl is shown to be isotypic with tetragonal BiOCl with lattice parameters a=b=4.079(2) A , c=6.837(2) A . The compound Ce 6 Cl 12 N 2 was prepared from CeCl 3 , Ce and NaN 3 in a sealed Nb tube at 750 °C. The structure of Ce 6 Cl 12 N 2 was solved by X-ray single crystal diffraction and shown to contain edge-shared, nitrogen-centered, cerium tetrahedra. The lattice parameters for Ce 6 Cl 12 N 2 were determined to be a=11.233(4) A , b=16.527(8) A , c=10.708(3) A , β=90.15° in the spacegroup P2 1 c .

Band gap and index of refraction of CsH to 251 GPa

Optical transmission and reflectivity measurements were made on CsH to 251 GPa. The index of refraction for CsH, obtained from reflectivity measurements, varied linearly with fractional density from 1.28 at zero pressure to 3.21 at 251 GPa. The band gap, estimated by the absorption edge, was found to be 4.4 eV at zero pressure and closed to 1.9 eV at 251 GPa.

The crystal structure of Sr6Cu3N5 with isolated, bent (Cu21N3)7− anions and the single crystal structural determination of SrCuN

Abstract Single crystals of the ternary nitrides Sr6Cu3N5 and SrCuN were prepared in high pressure autoclaves at 800 °C. Tetragonal crystals of the nitridocuprate, Sr6Cu3N5 crystallized in space group P42mc (no. 105), a=8.649(1) A , c=7.325(1) A . This compound represents a new structure type characterized by a mixture of linear (Cu1N2)3− and unprecedented V-shaped (Cu21N3)7− nitridometallate anions. The crystal structure of SrCuN was confirmed by single crystal data to adopt the BaNiN structure type (Pnma (no. 62), a=9.045(2), b=13.234(3), c=5.388(1) A ; Z=12).

CRYSTAL STRUCTURE AND BAND GAP OF RUBIDIUM HYDRIDE TO 120 GPa

Energy dispersive x ray diffraction measurements were performed on RbH to 120 GPa. RbH was observed to transform from the B2 phase to the orthorhombic, CrB, phase at 85 GPa. The equation of state for the B2 phase and the CrB phase are reported. Transmission measurements were made to 120 GPa to determine the band gap versus pressure in RbH. We report here the first measurement of the band gap of RbH at zero pressure at 4.91 eV. At 120 GPa, the band gap closed to 2.68 eV. Extrapolating the present band gap data leads to a zero gap at about 310 GPa.

Phonon reflectivity behavior in CsH and CsD at megabar pressures: Phonons in the near IR (λ = 1 – 2 μm)

Abstract Reflectivity at the diamond-sample interface was measured for CsH at P = 0, 102, 177 and 251 GPa and for CsD at 137 GPa in the energy range 0.5–2.5 eV. The expected isotope effect for phonons was found, confirming that the rise in reflectivity observed at high pressure and the near infrared as energy decrease is due to phonons and is not a plasma edge, which might also be expected in this pressure range for CsH. These are the first studies of phonon reflectivity in the diamond anvil cell to 2.5 Mbar and are the first high pressure phonon studies in any of the alkali hydrides.