“…The initial volume, V o of the rock salt structure PrN(I) is determined as 68.5(0.2) Å 3 (reduced to z=2), which agrees very well with the published value, ICDD database, PDF-2 #18-1077. However, 67.70 Å 3 was reported by Ettmayer et al [21] This value is 1% smaller than the present fit value. B o is estimated as 149(3) GPa.…”
“…The initial volume, V o of the rock salt structure PrN(I) is determined as 68.5(0.2) Å 3 (reduced to z=2), which agrees very well with the published value, ICDD database, PDF-2 #18-1077. However, 67.70 Å 3 was reported by Ettmayer et al [21] This value is 1% smaller than the present fit value. B o is estimated as 149(3) GPa.…”
“…The interatomic distances of Si−(O,N) resulted in the range of 1.635(7)−1.714(7) Å, which were comparable with the Si−(O,N) lengths of other silicon oxynitrides analyzed by the neutron diffraction method: Si 2 ON 2 , , 1.647−1.758 Å; Y 2 Si 3 O 3 N 4 , 1.661(8)−1.714(7) Å; Lu 4 Si 2 O 7 N 2 , 1.625(6)−1.697(5) Å. The La−(O,N) x interatomic distances in La 4 Si 2 O 7 N 2 (2.298(6)−2.903(5) Å) were close to those in La-contained oxides, oxynitrides, and nitrides: La 2 O 3 , , 2.372−2.841 Å; La 2 Si 2 O 7 , − 2.284−3.053 Å; La 4.67 (SiO 4 ) 3 O, 2.290−2.792 Å; La 10 (SiO 4 ) 6 N 2 , 2.316−2.843 Å; LaSiO 2 N, 2.453−2.618 Å; LaN, , 2.651−2.652 Å. 2 TOF neutron powder diffraction pattern and Rietveld refinement profile of La 4 Si 2 O 7 N 2 .…”
The polycrystalline single-phase sample of La 4 Si 2 O 7 N 2 was prepared at 1773 and 1873 K by the gas-pressured sintering method. The structure refinement was carried out by the Rietveld method using time-of-flight neutron powder diffraction data measured at 297 K. La 4 Si 2 O 7 N 2 is isostructural with the Y 4 Al 2 O 9 high-temperature phase and crystallizes in a monoclinic cell, P2 1 /c (No. 14-1), Z ) 4. The lattice parameters refined for the sample prepared at 1773 K were a ) 8.0375( 2) Å, b ) 10.9900(2) Å, c ) 11.1115(2) Å, and β ) 110.9214(14)°. Nitrogen atoms statistically occupy the bridging site and the terminal sites of Si 2 O 5 N 2 ditetrahedra in the La 4 Si 2 O 7 N 2 structure. The nonmetal sites surrounded by La atoms only are fully occupied by oxygen atoms.
“…There is neither long-range ordering nor a phase transition at or around 5 K (T N ). The specific heat is of the form C p = γT þ βT 3 , where γ is the electronic contribution and β is the lattice contribution. For the temperature range 10 K < T < 20 K, the data can be fit to afford the values γ = 336(3) mJ K -2 mol -1 and β = 1.00(1) mJ K -4 mol -1 .…”
The compound La(2)U(2)Se(9) was obtained in high yield from the stoichiometric reaction of the elements in an Sb(2)Se(3) flux at 1123 K. The compound, which crystallizes in a new structure type in space group Pmma of the orthorhombic system, has a three-dimensional structure with alternating U/Se and La/Se layers attached via three independent, infinite polyselenide chains. The U atom has a monocapped square antiprismatic coordination of Se atoms, whereas one La atom is bicapped square prismatic and the other La atom is trigonal prismatic. La(2)U(2)Se(9) displays an antiferromagnetic transition at T(N) = 5 K; above 50 K, the paramagnetic behavior can be fit to the Curie-Weiss law, yielding a mu(eff) of 3.10(1) mu(B)/U. The low-temperature specific heat of La(2)U(2)Se(9) exhibits no anomalous behavior near the Neel temperature that might indicate long-range magnetic ordering or a phase transition. X-ray absorption near-edge structure (XANES) spectra have confirmed the assignment of formal oxidation states of +III for lanthanum and +IV for uranium in La(2)U(2)Se(9).
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