No. 20112 Deposited at http://cryst.instr.yamaguchi-u.ac.jp/20112
Journal: Journal of the Physical Society Japan 80, No.6, pp.064602 (June 2011)
Title: Structural Study of Ordering at the Normal-Commensurate Transition of
{N(CH3)4}2MnCl4
Authors: N. Koshiji* & H. Mashiyama
Affiliation: Fuculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan and
Kurume National College of Technology, Kurume, Fukuoka 830-8555, Japan
(Received September 18, 2010)
Abstract:
The ordering process of constituent molecules in phase III of {N(CH3)4}2MnCl4 is discussed on the basis of the
results of X-ray structural analyses performed at nine temperatures below the normal-commensurate transition point.
The order-disorder and displacive models are analyzed and compared in terms of the temperature dependences of
structural parameters. Consequently, it is concluded that both tetramethylammonium and tetrachloromanganese ions
behave as order-disorder units, and that their occupation probability, representative of the order parameter, changes
monotonically with decreasing temperature. The results of our detailed analysis indicate that the centers of mass of the
tetrahedral molecules shift continuously together with occupation ordering. The temperature dependence of the atomic
displacement parameters is also investigated to confirm that the transition is of the order-disorder type.
Keywords: commensurate phase, structure analysis, split atom method, occupation probability, structural phase
transition
* Corresponding author, e-mail: koshi(at)kurume-nct.ac.jp
DEPOSITED DATA (Phase III: 289K)