Abstract
The room temperature structure (P63/m) of apatite compounds can be viewed as a distortion from a higher symmetry structure having space group P63/mcm. The distortion has a (+) or (−) sense corresponding to observed twinning in Cd5(PO4)3Cl. A specific high symmetry structure is obtained by taking the half way positions in switching from (+) to (–) domains. Energy considerations are made which (1) predict that the structure of microcrystals is closer to the high symmetry phase than larger samples and (2) explain why twinning of this sort is more likely in Cd5(PO4)3Cl than Ca5(PO4)3F. Finally, the transition from high to low symmetry is discussed in terms of a „frozen in” soft phonon of the high symmetry phase. It is shown that the soft mode must have A2g symmetry.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
