Researchers at EPFL have made significant progress in understanding the electronic properties of water, a fundamental component of life and the environment. There is no doubt that water is of great importance. Since oceans cover more than 70% of the Earth, without it, life would never have arisen, let alone continue today, let alone its role in the environment.

But despite its ubiquity, liquid water has some electronic subtleties that have long puzzled scientists in chemistry, physics and technology. For example, the electron affinity, that is, the stabilization of the energy experienced by a free electron when captured by water, has not been adequately characterized from an experimental point of view.

We solve the electronic mysteries of water

Even the most accurate current theory of electronic structure has failed to clarify the picture; This means that important physical quantities, such as the energy at which electrons from external sources can be injected into liquid water, are difficult to understand. These properties are critical for understanding the behavior of electrons in water and may play a role in biological systems, ecological cycles, and technological applications such as solar energy conversion.

In a recent study, EPFL researchers Oleksiy Tal, Thomas Bischoff and Alfredo Pascarello made significant progress in deciphering the puzzle. His work has been published in the journal: PNAS examines the electronic structure of water using computational methods that go beyond current approaches.

Advanced theoretical approaches

The researchers studied water using a method based on “multibody perturbation theory.” It is a complex mathematical system used to study the interaction of many particles in a system, such as electrons in a solid or molecule, by examining how these particles affect each other’s behavior not individually but as part of a larger interacting group. . In relatively simple terms, many-body perturbation theory is a way to calculate and predict the properties of a multi-particle system by taking into account all the complex interactions between its components.

But physicists have modified the theory with “vertical corrections”: modifications of many-body perturbation theory that explain complex interactions between particles beyond the simplest approximations. Vertex corrections improve the theory by taking into account how these interactions affect the energy levels of the particles (e.g., their response to external fields or their own energy). In short, corner corrections lead to more accurate predictions of the physical properties of a multiparticle system.

Modeling the electronic properties of water

Liquid water is particularly difficult to model. A water molecule contains one oxygen atom and two hydrogen atoms, and both their thermal motion and the quantum nature of their nuclei play an important role. Taking these aspects into account, researchers have precisely determined the electronic properties of water, such as ionization potential, electron affinity and band gap. These findings are important for understanding how water interacts with light and other substances at the electronic level.

“Our study of the energy level of water combines high-level theory with experiment,” says Alfredo Pasquarello. Oleksiy Tal also emphasizes the importance of the new methodology: “Thanks to the expanded description of the electronic structure, we were also able to obtain an accurate absorption spectrum.”

A new paradigm in materials science

The findings have additional implications. The theoretical advances implemented by the EPFL team form the basis of a new universal standard for achieving the precise electronic structure of materials. This provides a highly predictive tool that could potentially revolutionize our fundamental understanding of electronic properties in condensed matter science, with applications to finding properties of materials with specific electronic functions.