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A simulation at the molecular level showing a detailed explanation of the water anomaly

Research team of IBM, in collaboration with the research laboratory of the British Council for Science and Technology, developed a new type of material simulation that allows to improve the predictability of the durability of the materials in different situations and models.

In the picture: an illustration of the arrangement of water molecules at temperatures around the freezing point, arranged around a single reference molecule. The white area shows the orderly and directional organization of the water density in the form of an "oyster", which results from the properties of the bonds between the hydrogen molecules. The orange color shows a "volume increase area", which a water molecule cannot penetrate, due to its structural characteristics. Source: IBM.
In the picture: an illustration of the arrangement of water molecules at temperatures around the freezing point, arranged around a single reference molecule. The white area shows the orderly and directional organization of the water density in the form of an "oyster", which results from the properties of the bonds between the hydrogen molecules. The orange color shows a "volume increase area", which a water molecule cannot penetrate, due to its structural characteristics. source: IBM.

Materials used in industrial and engineering systems - such as iron and steel - are often exposed to high temperatures and extreme pressures, in complex environments where the properties of these materials may change substantially compared to the properties we are familiar with under normal circumstances.

One of the most famous examples of this phenomenon is the outer coating of the space shuttle Columbia, which was built of bricks that combine silica (sand) with aluminum oxide - in order to protect against extreme temperatures. Looking back, it's hard to believe how the engineers managed to meet this goal, given the limited amount of computing power at their disposal.

The possibility of predicting the behavior of materials, such as these cladding materials, under conditions fundamentally different from those of the everyday environment, and when the experimental possibilities are inherently limited, constitutes a fundamental advance in the world of planning and discovering new materials. Here, a unique challenge arises for the simulation of materials - which requires particularly complex models.

A team of IBM researchers, in collaboration with the research laboratory of the British Council for Science and Technology, has developed a new type of material simulation, which makes it possible to improve predictability and expands the range of situations to which the models of the material refer at the molecular level. Going down to this basic level allows for a more accurate prediction: the integration of a model that predicts the reaction at the level of the electrons of the single atom, allows the simulation to behave as if it were such a real single molecule - and to analyze the way it reacts within a larger and more complex system.

The anomaly of water: in the transition between liquid and ice, water increases its volume - contrary to the behavior we are familiar with in other substances, which tend to shrink and lose their volume as they cool. This is why, for example, ice floats - because its density is lower than liquid water. Illustration: pixabay.
The anomaly of water: in the transition between liquid and ice, water increases its volume - contrary to the behavior we are familiar with in other substances, which tend to shrink and lose their volume as they cool. This is the reason, for example, that ice floats - because its density is lower than that of liquid water. Illustration: pixabay.

In a scientific article published this month in Nature Scientific Reports, the researchers explain - with the help of this model - the mysterious behavior of water, close to the freezing point. The water anomaly Well known to anyone who forgot a glass bottle full of water in the freezer compartment of their refrigerator and discovered that the bottle exploded due to the volume expansion of the water that occurs around the freezing point. In the transition between liquid and ice, the water increases its volume - contrary to the behavior we are familiar with in other substances, which tend to shrink and lose their volume as they cool.

The researchers performed a simulation of the water in order to examine the molecular properties at the end of the temperature range where water exhibits structural stability: at the upper end of this range, the water is compressed into small chains of molecules, forming droplets whose temperature drops to the lowest achievable within this structure of a cold liquid Especially - which is significantly lower than the stagnation point. Later, they pass and arrange themselves in a "stretched" structure - when the bonds between the liquid molecules support high pressures, before they "break" in order to create characteristic curves. The work also revealed previously unknown connections between the molecular structure of the liquid and what is known as "amorphous ice" - with a texture reminiscent of ice cream that has been thawed and refrozen unevenly.

The success recorded by the model in predicting the behavior of water in the real world provides proof of the effectiveness of the simulation method at the level of the single molecule that forms the basis of this model. Although the model presented in the article is applied to liquids - its guiding principles can be put to practical use in the world of solid materials, and now IBM is developing new applications of it, in the field of life sciences.

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