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A commensurately modulated crystal structure and the physical properties of a novel polymorph of the caesium manganese phosphate CsMnPO 4
Author(s) -
Bolotidezhda,
Yakubovich Olga,
Shvanskaya Larisa,
Dimitrova Olga,
Volkov Anatoly,
Vasiliev Alexander
Publication year - 2019
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520619009296
Subject(s) - crystallography , tridymite , monoclinic crystal system , crystal structure , manganese , hydrothermal synthesis , rubidium , chemistry , isostructural , flux method , tetrahedron , antiferromagnetism , phase (matter) , caesium , materials science , single crystal , hydrothermal circulation , inorganic chemistry , cristobalite , physics , quartz , potassium , condensed matter physics , organic chemistry , seismology , composite material , geology
A novel modification of the CsMnPO 4 β‐phase was achieved by hydrothermal synthesis at 553 K. The compound crystallizes in the monoclinic system with the basic unit‐cell parameters a = 11.0699 (4), b = 11.0819 (6), c = 9.1106 (3) Å, γ = 119.480 (5) o ; the modulation vectors are q1 = 0.4 a * and q2 = 0.4 b *. The structure was determined based on single‐crystal X‐ray diffraction data obtained from a pseudo‐merohedral twin using a superspace approach in the (3 + 2)D symmetry group P 11 a (a1,b1,0)0(a2,b2,0)0 and refined to R = 0.083 for 10 266 reflections with I > 3σ( I ). It is considered as a low‐temperature polymorph of CsMnPO 4 with the same UUUDDD ‐type layer topology built by MnO 4 and PO 4 tetrahedra, and stacked in a framework in the same manner as β‐tridymite. Large open channels parallel to the [110] and [001] directions incorporate Cs atoms. All Cs atoms are distributed along the a super = 55.35 (1) and b super = 55.41 (1) axes of the large unit cell with pseudo periods of a super /5 and b super /5 which are broken mainly by the positions of oxygen atoms (orientation of Mn‐ and P‐centered tetrahedra). The β‐phase is discussed as a member of the morphotropic series of manganese phosphates with large cations of A MnPO 4 , where A = Cs, Rb, K and Ag. The title compound is an antiferromagnet with the Neel temperature T N = 4.5 K.