Structure determination and reorientational disorder in two phases of Sr(ND2)2 and Ca(ND2)2

J. Senker; M. Müller; W. Press; H. M. Mayer; R. M. Ibberson; H. Jacobs

doi:10.1016/S0921-4526(96)00875-7

Structure determination and reorientational disorder in two phases of Sr(ND₂)₂ and Ca(ND₂)₂

J. Senker, M. Müller, W. Press, H. M. Mayer, R. M. Ibberson, H. Jacobs

Research output: Contribution to journal › Article › peer-review

5 Scopus citations

Abstract

Temperature-dependent neutron powder diffraction experiments were carried out on Sr(ND₂)₂ and Ca(ND₂)₂, both crystallizing in a tetragonal distorted anatase structure type, to determine the evolution of the temperature factors of all atoms. Amplitudes and geometry of librations were analysed using a rigid-body model. They fit well to results from line shape analyses of wideline ²H-NMR spectra and can be described as composed of strong rocking librations with weak temperature dependence and weak wagging librations with strong temperature dependence. The rapidly increasing amplitude of the wagging libration is correlated to an anomalous thermal expansion for both compounds. Furthermore, slow 180° reorientations about the C₂-axis of ND^-₂ were detected above RT. Below 70 resp. 100 K for Sr(ND₂)₂/Ca(ND₂)₂ a reduction of tetragonal to monoclinic symmetry was observed caused by an ordering of deuterons due to freezing the rocking libration.

Original language	English
Pages (from-to)	51-53
Number of pages	3
Journal	Physica B: Physics of Condensed Matter
Volume	234-236
DOIs	https://doi.org/10.1016/S0921-4526(96)00875-7
State	Published - Jun 2 1997
Externally published	Yes

Keywords

Crystal structures
Inorganic compounds
NMR
Phase transitions
Powder diffraction
Proton dynamics
Rietveld refinement

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10.1016/S0921-4526(96)00875-7

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title = "Structure determination and reorientational disorder in two phases of Sr(ND2)2 and Ca(ND2)2",

abstract = "Temperature-dependent neutron powder diffraction experiments were carried out on Sr(ND2)2 and Ca(ND2)2, both crystallizing in a tetragonal distorted anatase structure type, to determine the evolution of the temperature factors of all atoms. Amplitudes and geometry of librations were analysed using a rigid-body model. They fit well to results from line shape analyses of wideline 2H-NMR spectra and can be described as composed of strong rocking librations with weak temperature dependence and weak wagging librations with strong temperature dependence. The rapidly increasing amplitude of the wagging libration is correlated to an anomalous thermal expansion for both compounds. Furthermore, slow 180° reorientations about the C2-axis of ND-2 were detected above RT. Below 70 resp. 100 K for Sr(ND2)2/Ca(ND2)2 a reduction of tetragonal to monoclinic symmetry was observed caused by an ordering of deuterons due to freezing the rocking libration.",

keywords = "Crystal structures, Inorganic compounds, NMR, Phase transitions, Powder diffraction, Proton dynamics, Rietveld refinement",

author = "J. Senker and M. M{\"u}ller and W. Press and Mayer, {H. M.} and Ibberson, {R. M.} and H. Jacobs",

year = "1997",

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doi = "10.1016/S0921-4526(96)00875-7",

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T1 - Structure determination and reorientational disorder in two phases of Sr(ND2)2 and Ca(ND2)2

AU - Senker, J.

AU - Müller, M.

AU - Press, W.

AU - Mayer, H. M.

AU - Ibberson, R. M.

AU - Jacobs, H.

PY - 1997/6/2

Y1 - 1997/6/2

N2 - Temperature-dependent neutron powder diffraction experiments were carried out on Sr(ND2)2 and Ca(ND2)2, both crystallizing in a tetragonal distorted anatase structure type, to determine the evolution of the temperature factors of all atoms. Amplitudes and geometry of librations were analysed using a rigid-body model. They fit well to results from line shape analyses of wideline 2H-NMR spectra and can be described as composed of strong rocking librations with weak temperature dependence and weak wagging librations with strong temperature dependence. The rapidly increasing amplitude of the wagging libration is correlated to an anomalous thermal expansion for both compounds. Furthermore, slow 180° reorientations about the C2-axis of ND-2 were detected above RT. Below 70 resp. 100 K for Sr(ND2)2/Ca(ND2)2 a reduction of tetragonal to monoclinic symmetry was observed caused by an ordering of deuterons due to freezing the rocking libration.

AB - Temperature-dependent neutron powder diffraction experiments were carried out on Sr(ND2)2 and Ca(ND2)2, both crystallizing in a tetragonal distorted anatase structure type, to determine the evolution of the temperature factors of all atoms. Amplitudes and geometry of librations were analysed using a rigid-body model. They fit well to results from line shape analyses of wideline 2H-NMR spectra and can be described as composed of strong rocking librations with weak temperature dependence and weak wagging librations with strong temperature dependence. The rapidly increasing amplitude of the wagging libration is correlated to an anomalous thermal expansion for both compounds. Furthermore, slow 180° reorientations about the C2-axis of ND-2 were detected above RT. Below 70 resp. 100 K for Sr(ND2)2/Ca(ND2)2 a reduction of tetragonal to monoclinic symmetry was observed caused by an ordering of deuterons due to freezing the rocking libration.

KW - Crystal structures

KW - Inorganic compounds

KW - NMR

KW - Phase transitions

KW - Powder diffraction

KW - Proton dynamics

KW - Rietveld refinement

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U2 - 10.1016/S0921-4526(96)00875-7

DO - 10.1016/S0921-4526(96)00875-7

M3 - Article

AN - SCOPUS:18344408401

SN - 0921-4526

VL - 234-236

SP - 51

EP - 53

JO - Physica B: Physics of Condensed Matter

JF - Physica B: Physics of Condensed Matter

ER -

Structure determination and reorientational disorder in two phases of Sr(ND₂)₂ and Ca(ND₂)₂

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Keywords

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