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Crystal Structure of the High Pressure Phase(II) in CuGeO 3
Author(s) -
Yoshiasa Akira,
Yagyu Genta,
Ito Tomokazu,
Yamanaka Takamitu,
Nagai Takaya
Publication year - 2000
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/(sici)1521-3749(200001)626:1<36::aid-zaac36>3.0.co;2-2
Subject(s) - crystallography , monoclinic crystal system , phase transition , crystal structure , hydrostatic pressure , phase (matter) , ambient pressure , isostructural , ion , crystal (programming language) , lattice (music) , chemistry , tetragonal crystal system , materials science , condensed matter physics , physics , thermodynamics , organic chemistry , computer science , acoustics , programming language
Crystal structures of the ambient pressure and temperature phase (phase I) and high pressure phase (phase II) in CuGeO 3 were studied by means of the high pressure single‐crystal X‐ray diffraction method in a diamond anvil cell using high power X‐ray generator and imaging plate detector. The pressure dependence of the atomic displacements in the phase I was investigated under the hydrostatic pressure of 0.1 MPa and 2.9 and 3.9 GPa. The lattice is particularly compressive in the b direction. In phase I the rippled layers are formed by the corner‐shared chains of GeO 4 tetrahedra and edge‐linked planar CuO 4 . Major effects of pressure, directly related to the shortening of the b‐axis, consist of an enhanced folding of the rippled layers towards the b‐direction and of a shortening of the weak Cu–O bond. The crystal structure of phase II is monoclinic, a = 4.935(57), b = 6.754(14), c = 6.208(11) Å, β = 92.67(3)°, space group; P2 1 /c. The transition from phase I to II involves a corrugated arrangement of the both cation with some oxygens around the c‐axis. Ge ion at the transition point of 6.4 GPa changes its coordination number from four‐fold to five‐fold, and Cu ion occupies a position of seven‐fold site. The structure of phase II is explained as a slab structure having unique edge‐ and corner‐sharing arrangements of GeO 5 and CuO 7 polyhedra. The average Ge–O and Cu–O distances in phase II is 1.92 and 2.17 Å, respectively, at 6.5 GPa.