Digitale Medien
College Park, Md.
:
American Institute of Physics (AIP)
The Journal of Chemical Physics
85 (1986), S. 6004-6009
ISSN:
1089-7690
Quelle:
AIP Digital Archive
Thema:
Physik
,
Chemie und Pharmazie
Notizen:
The crystal structures of the high temperature (paraelastic) and low temperature (ferroelastic) phases of the cyanospinel K2Hg(CN)4 have been determined by neutron powder diffraction. At 298 K the crystal has the spinel structure and the cyanide coordination is ordered in the sequence N–C–Hg–C–N. Below the phase transition (111 K) the structure is trigonal with space group R3¯c. At the transition Hg(CN)4 tetrahedra adjacent along [111] rotate in antiphase as rigid units by ≈7° and the K ion shifts by ≈0.1A(ring). The transition has an ordering wave vector q0≡{1/2 1/2 1/2}. Comparison is made with the structural characteristics of other cyanospinels and it is suggested that the transitions cannot be understood in terms of steric interactions but must be a dynamic effect.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.451514
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