Abstract
Some liquids, if cooled rapidly enough to avoid crystallization, can be frozen into a nonergodic glassy state. The tendency for a material to form a glass when quenched is called “glass-forming ability,” and it is of key significance both fundamentally and for materials science applications. Here, we consider liquids with competing orderings, where an increase in the glass-forming ability is signaled by a depression of the melting temperature towards its minimum at triple or eutectic points. With simulations of two model systems where glass-forming ability can be tuned by an external parameter, we are able to interpolate between crystal-forming and glass-forming behavior. We find that the enhancement of the glass-forming ability is caused by an increase in the structural difference between liquid and crystal: stronger competition in orderings towards the melting point minimum makes a liquid structure more disordered (more complex). This increase in the liquid-crystal structure difference can be described by a single adimensional parameter, i.e., the interface energy cost scaled by the thermal energy, which we call the “thermodynamic interface penalty.” Our finding may provide a general physical principle for not only controlling the glass-forming ability but also the emergence of glassy behavior of various systems with competing orderings, including orderings of structural, magnetic, electronic, charge, and dipolar origin.
- Received 18 August 2017
- Revised 1 February 2018
DOI:https://doi.org/10.1103/PhysRevX.8.021040
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Some liquids, if cooled rapidly enough to avoid crystallization, can be frozen into a glassy state—a relatively hard and brittle amorphous solid. Materials in which glass formation is crucial include organic materials, silicon, water, oxides, metals, and semiconductors. A material’s glass-forming ability is characterized by the minimum cooling rate necessary for its glass transformation. Elucidating the physical origin of this ability is of key significance to materials science applications as well as to fundamental physics. So far, descriptions of glass-forming ability have been based largely on empirical rules. Using numerical simulations, we explore glass-forming ability in two model systems.
We find that glassiness stems from the loss of ordered regions in the liquid phase. Contrary to common belief, the structure in a glass-forming liquid is not random but gains more and more structural order upon cooling. How close the liquid structure is to the crystalline structure determines the glass-forming ability: Less similarity leads to greater glass-forming ability.
Our finding will provide a general physical principle for understanding the emergence of glassy behavior for a class of systems with competing orderings—including those of structural, magnetic, electronic, charge, and dipolar origin—and also contribute to material design for glass formation.
