Journal ArticleDOI
Modulated structure of thiourea [SC ( N H 2 ) 2 ]
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TLDR
In this paper, a group-theoretical consideration and detailed structure analysis have been made of the incommensurate phase of thiourea, showing that extinction rules observed by neutron diffraction imply condensation of even-order harmonics.Abstract:
To verify the condensation of higher-order harmonics of the soft mode in incommensurate phase, group-theoretical consideration and detailed structure analysis have been made of the incommensurate phase of thiourea. The group-theoretical consideration shows that extinction rules observed by neutron diffraction imply condensation of even-order harmonics. An analysis based on a four-dimensional space group also confirms the condensation of the second-order harmonics.read more
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Journal ArticleDOI
Experimental studies of structurally incommensurate crystal phases
Journal ArticleDOI
Incommensurate crystal structures
TL;DR: An overview of the crystallography of aperiodic crystals, in particular of incommensurately modulated structures and intergrowth compounds, is given in this paper, where the symmetry, the description of the structure and diffraction are described.
Journal ArticleDOI
Incommensurability in crystals
T.J.B.M. Janssen,A. Janner +1 more
TL;DR: In this paper, the authors present aperiodic crystals from a unifying point of view, showing why it is justified to call them crystals, despite the lack of a three-dimensional lattice periodicity, and discuss in what sense they differ from periodic crystals in structure, symmetry and other physical properties.
Journal ArticleDOI
Aperiodic crystals and superspace concepts
T.J.B.M. Janssen,A. Janner +1 more
TL;DR: In the early sixties of the last century compounds were found which for many reasons should be called crystals, but were not lattice periodic, which opened the field of aperiodic crystals.
Journal ArticleDOI
Dielectric and light scattering spectroscopy of incommensurate phases in crystals
TL;DR: In this paper, a review of all the corresponding experimental data published up to the middle of 1980 are reviewed and consistently interpreted taking into account the specific selection rules recenily derived.
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