title: Classical and quantum molecular dynamics of cation in (CH3NH3)3 Sb2Br9 polycrystal as studied by 1H NMR.
abstract: 1H spin-lattice relaxation times and second moments were determined for polycrystalline (CH3NH3)3Sb2Br9 sample in a wide range of temperature (5-200 K) at 24.6 and 55.2 MHz. 2H NMR spectra of (CD3NH3)3Sb2Br9 were recorded between 5 K and room temperature. The relaxation time is interpreted as a result of motion of two different non-equivalent types of monomethylammonium cations occurring at the 2:1 proportion in a unit cell. Below 30 K, the relaxation processes via tunneling are suggested to dominate. Above 30 K, only classical behaviour of methylammonium cations is detected. Two monomethylammonium cations relax with the classical correlated C3 reorientation and the rotational tunnelling mechanism, while the third cation exhibits only the classical correlated reorientation. The dynamic parameters of these motions have been determined.
authors.affiliation: Institute of Molecular Physics, PAS, Poznań, Poland. wojciech.medycki@ifmpan.poznan.pl
authors.forename: W
authors.initials: W
authors.lastname: Medycki
mesh_terms: D002412:Cations; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003460:Crystallization; D009682:Magnetic Resonance Spectroscopy; D008744:Methylamines / Q000032:analysis*; D011789:Quantum Theory; D013696:Temperature
chemical_list: D002412:Cations; D008744:Methylamines; C027451:methylamine