MATERIALS SCIENCE AND CHEMISTRY

Water is called the substance of life: it covers most of the planet, it constitutes the largest fraction of our body, we drink it every day. Water actively participates in most chemical processes in nature, and will be the source of Hydrogen as we transition to clean and renewable energy. Surprisingly, and despite its abundance and importance, water is still poorly understood. In fact, more than 100 anomalous properties of water are known, water ice floating on liquid water being the most eye-catching one. The origin of the complexity is the subtle forces between water molecules, which derive from electrostatic, repulsive, hydrogen bonding, and van der Waals interactions. Getting the balance between these forces right is key for all of soft matter, and the sensitivity of water makes it the ideal testcase.

Computing the interactions between electrons and atoms requires solving the laws of quantum mechanics, the Schrödinger equation, accurately enough to capture the fine features. For almost 100 years this has been a very active field of research, in which supercomputing is essential. In fact, the equation is computationally so demanding to solve, that even on the largest supercomputers only approximate solutions can be obtained. However, the resources available at HLRS gave the team lead by Prof. VandeVondele (ETH Zürich) the opportunity to make a significant step forward, enabling the next level of accuracy in such simulations. In particular, computational approaches that treat van der Waals interactions at equal footing with the other forces have been applied to bulk liquid water for the first time. Compared to more standard approaches, these theories require roughly 1000 times more computational power, and have only become possible with significant progress in hard- and software development. [1,2] Interestingly, the weak interactions they describe make all the difference.

Computing the interactions between electrons and atoms requires solving the laws of quantum mechanics, the Schrödinger equation, accurately enough to capture the fine features. For almost 100 years this has been a very active field of research, in which supercomputing is essential. In fact, the equation is computationally so demanding to solve, that even on the largest supercomputers only approximate solutions can be obtained. However, the resources available at HLRS gave the team lead by Prof. VandeVondele (ETH Zürich) the opportunity to make a significant step forward, enabling the next level of accuracy in such simulations. In particular, computational approaches that treat van der Waals interactions at equal footing with the other forces have been applied to bulk liquid water for the first time. Compared to more standard approaches, these theories require roughly 1000 times more computational power, and have only become possible with significant progress in hard- and software development.[1,2] Interestingly, the weak interactions they describe make all the difference.