N.E. Brese

Bond-valence parameters for solids

Bond-valence parameters which relate bond valences and bond lengths have been derived for a large number of bonds. It is shown that there is a strong linear correlation between the parameters for bonds from cations to pairs of anions. This correlation is used to develop an interpolation scheme that allows the estimation of bond-valence parameters for 969 pairs of atoms. A complete listing of these parameters is given.

Synthesis, crystal structure, and physical properties of Sr2N

Abstract Sr2N has been synthesized from the elements and its structure determined by time-of-flight neutron diffraction. Crystal data: R 3 m, a = 3.8566(1) A, c = 20.6958(4) A, V = 266.58(1) A3, Z = 3, Dx = 2.13, T = 300 K, Rwp = 0.077, Rp = 0.056, reduced χ2 = 2.06 for 25,368 profile points and 53 variables. Sr2N crystallizes with the layered CdCl2 structure as formerly proposed. N atoms center flattened octahedra with six equal NSr distances of 2.6118(3) A. The SrSr distances in the octahedral layer are 3.8566(1) (6x) and 3.523(1) (3x). The SrSr distances between layers are 4.726(1). It has been argued that Sr2N is actually Sr2NxHy; but the neutron data show the absence of any hydrogen contamination. Sr2N is a metallic conductor with a weak temperature-independent paramagnetism.

Crystal structures of NaCuO2 and KCuO2 by neutron diffraction

Abstract The structures of NaCuO 2 and KCuO 2 have been refined from time-of-flight neutron data. NaCuO 2 is monoclinic: space group C2 m , a = 6.3512(2) A, b = 2.7474(1)A, c = 6.1027(2)A, β = 120.767(2)° with CuO = 1.839(1) A (4×). KCuO 2 is orthorhombic: space group Cmcm , a = 4.3742(1)A, b = 11.6859(4)A, c = 5.4124(2)A with CuO = 1.826(3) A (2×) and 1.832(2) A (2×). Both structures contain strings of edge-sharing CuO 4 rectangles. The sodium atoms center octahedra and the potassium atoms center trigonal prisms. Aspects of the crystal chemistry of both compounds are discussed.

Low-temperature structures of CuO and AgO and their relationships to those of MgO and PdO

Abstract The CuO structure has been refined from time-of-flight neutron diffraction data collected at 11 K. Crystal data: C2 c , a = 4.6833(2) A, b = 3.4208(1) A, c = 5.1294(2) A, β = 99.567(1)°, V = 81.031(7)A3. The CuO distances are 1.951(1) and 1.961(1) A (each 2 ×) with corresponding OCuO angles of 84.315(7)° and 95.685(7)°. Data for a mixture of AgO and Ag2SO4 were collected at 9 K. Crystal data for AgO: P2 1 c , a = 5.8517(3) A, b = 3.4674(2) A, c = 5.4838(3) A, β = 107.663(3)°, V = 106.02(1)A3. The formula for AgO is better written as Ag(I)Ag(III)O2. The Ag(III) atoms are 4-coordinated: AgO = 2.008(3) (2x) and 2.036(3) (2x), and the Ag(I) atoms are 2-coordinated by O: AgO = 2.147(3) (2x). A comparison of the CuO, AgO, PdO, and MgO structures is presented.

Synthesis and crystal structure of SrD2 and SrND and bond valence parameters for hydrides

A mixture of SrD{sub 2} and SrND was obtained from a reaction of Sr{sub 2}N and D{sub 2}. Their structures were refined using time-of-flight neutron diffraction data. SrD{sub 2} and SrND crystallize with the PbCl{sub 2} and rock salt structures, respectively. For SrND the space group is Fm3m, a = 5.4474(1) {angstrom}. The diffraction data confirm the composition SrND and indicate a rotationally disordered ND group. For SrD{sub 2}, the prototype of the C29 structure type, the space group is Pnma, a = 6.3706(4) {angstrom}, b = 3.8717(2) {angstrom}, c = 7.3021(4) {angstrom}. The structure differs only in minor details from the C23 (PbCl{sub 2}) type.

Synthesis and Neutron Diffraction Study of Na3WN3 and Na3MoN3

We have used our ambient pressure method for the synthesis of ternary alkali metal nitrides to synthesize a new class of nitrides, Na3MN3 (M = Mo or W). These compounds were synthesized from the metal nitride and NaNH2 at 500°C under flowing ammonia at atmospheric pressure. The structures were examined using X-ray powder diffraction and neutron powder diffraction and were found to be identical with that obtained from the single crystal prepared at high pressure by Ostermann, Zachwieja, and Jacobs.

Synthesis and neutron diffraction study of Na[sub 3]WN[sub 3] and Na[sub 3]MoN[sub 3]

We have used our ambient pressure method for the synthesis of ternary alkali metal nitrides to synthesize a new class of nitrides, Na3MN3 (M = Mo or W). These compounds were synthesized from the metal nitride and NaNH2 at 500°C under flowing ammonia at atmospheric pressure. The structures were examined using X-ray powder diffraction and neutron powder diffraction and were found to be identical with that obtained from the single crystal prepared at high pressure by Ostermann, Zachwieja, and Jacobs.

Regular ArticleSynthesis and Neutron Diffraction Study of Na3WN3 and Na3MoN3

We have used our ambient pressure method for the synthesis of ternary alkali metal nitrides to synthesize a new class of nitrides, Na3MN3 (M = Mo or W). These compounds were synthesized from the metal nitride and NaNH2 at 500°C under flowing ammonia at atmospheric pressure. The structures were examined using X-ray powder diffraction and neutron powder diffraction and were found to be identical with that obtained from the single crystal prepared at high pressure by Ostermann, Zachwieja, and Jacobs.