At the Institute of Industrial Science at the University of Tokyo, molecular dynamics simulations were utilized by the researchers to better comprehend the exceptional properties of amorphous solids, like glass.
Certain dynamical defects were noted by the scientists, which would help describe the enabled vibrational modes within the material. This work might result in controlling the properties of amorphous materials.
At times, high-priced glass is advertised as “crystal,” but to material scientists, this could not be far from the truth. The formation of crystals is done by atoms that are arranged in orderly and repeating patterns, while glass is in the form of a disordered and amorphous solid.
Researchers are well aware that, at low temperatures, several disordered materials exhibit properties that are quite similar to each other, such as particular heat and thermal conductivity. Such properties tend to vary considerably from those of materials that are created from ordered crystals.
Additionally, at some frequency range, glassy materials consist of a bigger number of available vibration modes compared to crystals, known in the field as the “boson peak.” While numerous theories have been suggested, the basic physical mechanisms for such observations have been a question of active research.
Currently, researchers from The University of Tokyo have utilized sophisticated molecular dynamics computer simulations to numerically evaluate the transverse and longitudinal dynamic structure factors of model glasses over an extensive range of frequencies.
They discovered that string-like vibrational motions, in which curved lines of particles packed into a so-called “C” shape inside the material could move together, were discovered to be significant drivers of the anomalous effects.
These dynamical defects provide a common explanation for the origin of the most fundamental dynamic modes of glassy systems.
Yuan-Chao Hu, Study First Author, Institute of Industrial Science, The University of Tokyo
Besides the boson peak, such string-like dynamic defects could commit the kinds of slow and fast-slow relaxation that have been noted in the particles that develop the glass.
This study has several significant implications for both basic science and industrial applications due to the boson peak being discovered in several systems and not just glasses.
We show that the boson peak originates from quasi-localized vibrations of string-like dynamical defects.
Hajime Tanaka, Study Senior Author, Institute of Industrial Science, The University of Tokyo
Being able to describe this feature will provide new insight into several other kinds of disordered materials. Also, it will profit several users of smart devices. This is done since nearly all tablets, smartphones, and touchscreen laptops depend on glass materials so the outcomes of this study could be enhanced further.
Hu, Y-C & Tanaka, H (2022) Origin of the boson peak in amorphous solids. Nature Physics. doi.org/10.1038/s41567-022-01628-6