A new modification of thallium chromate related to the beta-K2SO4 family.
The title structure is a new modification of Tl(2)CrO(4). There are four independent Tl(+) cations and two [CrO(4)](2-) anions in the structure. It is closely related to the already known modification, which belongs to the beta-K(2)SO(4) family with two independent cations and one anion. In both modifications, the cations and anions are situated on crystallographic mirror planes. The volume of the asymmetric unit of the title structure is approximately 0.4% smaller than that of the known modification belonging to the beta-K(2)SO(4) family. The other difference between the two modifications is seen in the environment of the cations. In the title structure, none of the Tl(+) cations is underbonded, in contrast with the modification isostructural with beta-K(2)SO(4). In the beta-K(2)SO(4) family with simple cations, underbonding of one of the constituent cations is typical. The dependence of the unit-cell parameters on temperature does not indicate a phase transition in the interval 90-300 K.
Fábry
Jan
J
Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 182 21 Praha 8, Czech Republic. fabry@fzu.cz
Dusek
Michal
M
Fejfarová
Karla
K
Krupková
Radmila
R
Vanek
Premysl
P