Anharmonicity and isomorphic phase transition: a multi-temperature X-ray single-crystal and powder diffraction study of 1-(2 `-aminophenyl)-2-methyl-4-nitroimidazole
PBN-AR
Instytucja
Wydział Chemii (Uniwersytet Warszawski)
Informacje podstawowe
Główny język publikacji
en
Czasopismo
IUCrJ
ISSN
2052-2525
EISSN
Wydawca
International Union of Crystallography
DOI
URL
Rok publikacji
2014
Numer zeszytu
2
Strony od-do
110-118
Numer tomu
1
Identyfikator DOI
Liczba arkuszy
Streszczenia
Język
en
Treść
The harmonic model of atomic nuclear motions is usually enough for multipole modelling of high-resolution X-ray diffraction data; however, in some molecular crystals, such as 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole [Paul, Kubicki, Jelsch et al. (2011). Acta Cryst. B67, 365-378], it may not be sufficient for a correct description of the charge-density distribution. Multipole refinement using harmonic atom vibrations does not lead to the best electron density model in this case and the so-called `shashlik-like' pattern of positive and negative residual electron density peaks is observed in the vicinity of some atoms. This slight disorder, which cannot be modelled by split atoms, was solved using third-order anharmonic nuclear motion (ANM) parameters. Multipole refinement of the experimental high-resolution X-ray diffraction data of 1-(2'-aminophenyl)-2-methyl-4-nitro-1H-imidazole at three different temperatures (10, 35 and 70 K) and a series of powder diffraction experiments (20 <= T <= 300 K) were performed to relate this anharmonicity observed for several light atoms (N atoms of amino and nitro groups, and O atoms of nitro groups) to an isomorphic phase transition reflected by a change in the b cell parameter around 65 K. The observed disorder may result from the coexistence of domains of two phases over a large temperature range, as shown by low-temperature powder diffraction.
Cechy publikacji
discipline:Biochemia – dziedzina nauk chemicznych
discipline:Chemia
discipline:Technologia chemiczna – dziedzina nauk chemicznych
discipline:Biochemistry – field of chemical sciences
discipline:Chemistry
discipline:Chemical Technology – field of chemical sciences
Original article
Original article presents the results of original research or experiment.
Oryginalny artykuł naukowy
Oryginalny artykuł naukowy przedstawia rezultaty oryginalnych badań naukowych lub eksperymentu.
Inne
System-identifier
PBN-R:763924
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