Neutron quasielastic scattering by (CH3NH3)5Bi2Cl11

(CH3NH3)(+)-cation rotation in crystalline (CH3NH3)(5)Bi2Cl11 was studied by the QNS. The following (no doubt simplified) models were considered: 1. All cations are equivalent and rotate as a whole around C-N axes 2. Majority of cations behave as in point (1) and the remaining ones do not move (for the neutron observation window). 3. All CH3 groups rotate, whereas all NH3 groups do not move. The QNS measurements exclude the possibilities (1) and (3). A transition at ca. 160-170 K was confirmed in the measurements, as connected with an increase of the quasielastic component intensity observed via a dip of the EISF. (C) 1998 Elsevier Science B.V. All rights reserved.