ABSTRACT: Several trihalides (Cl, Br, I) of elements of groups 4, 5, 6, and 8 of the periodic table, such as TiI3, show a crystal structure made by parallel infinite columns, running along c, of face-sharing octahedra [MX6]. The metals placed within the columns may interact with one of the nearest neighbors, so that long and short MM distances regularly alternate along the columns; two distinct conformations are possible for the columns, one with M-M pairs centered at z = 1/4, the other with M-M pairs centered at z = 3/4. Below a certain temperature the distribution of the two types of columns in the a,b plane is ordered, giving rise to an orthorhombic form, with space group Pnmm. Over this temperature a transition to a hexagonal form, with space group P63/mcm, is observed. We, through X-ray diffraction studies carried out at different temperatures, estimate this transition temperature for RuBr3 and MoBr3 crystals and show that the hexagonal form too consists of ordered columns, the...
|Autori:||S. MERLINO; LABELLA L; F. MARCHETTI; S. TOSCANI|
|Titolo:||Order-Disorder Transformation in RuBr3 and MoBr3: A Two-Dimensional Ising Model|
|Anno del prodotto:||2004|
|Digital Object Identifier (DOI):||10.1021/cm049235q|
|Appare nelle tipologie:||1.1 Articolo in rivista|