Related Experiment Video
Updated: Aug 7, 2026
08:55
Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
Defect-mediated melting in superheated noble gas crystals
1Dipartimento di Ingegneria Chimica e Materiali, Università di Cagliari, piazza d'Armi, I-09123 Cagliari, Italy. delogu@dicm.unica.it
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Molecular dynamics simulations reveal that defective atomic coordination triggers homogeneous melting in noble gases. The fraction of these defects and their clustering remain consistent across different species at the melting point.
Area of Science:
- Materials Science
- Thermodynamics
- Computational Physics
Background:
- Superheating allows materials to exist above their equilibrium melting point.
- Understanding the mechanisms of homogeneous melting is crucial for materials science.
- Noble gases provide a simple system to study fundamental melting phenomena.
Purpose of the Study:
- To investigate the mechanisms of homogeneous melting in pure noble gases at the superheating limit.
- To identify the structural factors that destabilize a crystal lattice and trigger melting.
- To compare simulation results with existing theoretical predictions.
Main Methods:
- Utilized molecular dynamics simulations for noble gas systems.
- Estimated heterogeneous melting points using crystalline systems with grain boundaries.
- Determined the superheating limit by simulating perfect crystalline bulk under gradual temperature increase.
- Employed static order parameter to monitor structural disordering.
- Analyzed the appearance and spatial correlation of atoms with defective coordination.
Main Results:
- Identified defective atomic coordination as a key factor in destabilizing the crystalline lattice.
- Observed that the relative number and spatial correlation of defective atoms play a fundamental role in triggering homogeneous melting.
- Found the fraction of defective atoms and their stringlike cluster length to be consistent across different noble gas species near the melting point.
- Determined the temperature at which the crystalline lattice collapses into a liquid.
Conclusions:
- Homogeneous melting in noble gases at the superheating limit is governed by the emergence and spatial organization of defective atomic coordination.
- The observed consistency in defect fraction and clustering suggests a universal mechanism for melting initiation in these systems.
- The findings provide insights into the fundamental processes of phase transitions and validate theoretical predictions.
Related Concept Videos
01:29Imperfections in Crystal Structure: Non-Stoichiometric Defects
Non-stoichiometric defects refer to a type of defect in the crystal structure of a compound where the ratio of its constituent elements deviates from the ideal stoichiometric ratio. There are two main types of non-stoichiometric defects: metal excess defects and metal deficiency defects.Metal excess defects occur when there is a slight surplus of metal ions than what is required by the stoichiometric ratio of the compound. For example, heating a sodium chloride crystal in sodium vapor results...
01:26Imperfections in Crystal Structure: Stoichiometric Point Defects
Schottky defects arise when some lattice points in a crystal, such as those in NaCl, remain unoccupied, creating lattice vacancies without disturbing the overall electrical neutrality of the crystal. This defect is common in ionic crystals where the positive and negative ions are similar in size, as seen in sodium chloride and cesium chloride. The presence of Schottky defects enables the crystal to conduct electricity to a small extent through an ionic mechanism. Electric fields cause nearby...
01:25Imperfections in Crystal Structure: Point, Line and Plane Defects
A perfect crystal, in theory, has a uniform structure with the same unit cell and lattice points throughout. However, any deviation from this periodic arrangement is known as an imperfection or defect. These defects can be categorized into three types: point, line, and plane defects.Point defects occur when there is a deviation from the ideal due to missing atoms, displaced atoms, or additional atoms. These imperfections might occur due to imperfect packing during crystallization or because of...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:54Noble Gases
The elements in group 18 are noble gases (helium, neon, argon, krypton, xenon, and radon). They earned the name “noble” because they were assumed to be nonreactive since they have filled valence shells. In 1962, Dr. Neil Bartlett at the University of British Columbia proved this assumption to be false.