Related Experiment Video
Updated: Aug 1, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
A reinterpretation of the phase transitions in Na2CO3
Alla Arakcheeva1, Gervais Chapuis
1Ecole Polytechnique Fédérale de Lausanne, Institut de Physique de la Matière Complexe, BSP, 1015 Lausanne, Switzerland. Alla.Arakcheeva@epfl.ch
Abstract:
Based on the structural data of phases alpha (hexagonal; 756-972 K), beta (monoclinic; 605-751 K), gamma (incommensurate, monoclinic; 295 K) and delta (lock-in, monoclinic; 110 K) of sodium carbonate, Na2CO3, we could draw a parallel between the phase transitions and the evolution of the second coordination sphere of the C atoms. The temperature-dependent structures observed in the beta phase are reproduced in the incommensurate gamma phase as a modulation wave, which relates to the content of the symmetrically equivalent {110} lattice planes in the alpha phase. By decreasing the temperature, the phase transitions are associated with a stepwise increase in the number of Na ions participating in the second coordination sphere of the C atoms. Over the full temperature range, this number increases from 3 to 7. The C-O distances and the mobility of the O atoms depends on the number of Na ions in the vicinity of the C atoms.
Related Concept Videos
Phase Transitions: Melting and Freezing
Phase Transitions: Sublimation and Deposition
Phase Diagrams
Phase Changes
A substance melts or freezes at a temperature called its melting point and boils or condenses at its boiling point. These temperatures depend on pressure. High pressure favors the denser form of the substance, so typically, high pressure...
Phase Diagram
Phase Diagram

