A groundbreaking discovery by a team of researchers led by Professor Pavel Jungwirth at the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague) is poised to reshape our fundamental understanding of phase transitions between metallic and nonmetallic states in liquids. This research reveals a hitherto unknown dynamic phase that emerges transiently when certain liquids undergo transformation from nonmetallic to metallic conductors. Unlike traditional models which portray this transition as a static shift, the new findings propose a rapid, intrinsic oscillation between metallic and nonmetallic phases occurring at astonishingly brief timescales, measured in tens of femtoseconds. The team’s theoretical work, based on advanced molecular modeling and high-level computational simulations, not only challenges established concepts but also suggests new experimental directions for detecting these ultrafast phenomena.
The transition from a nonmetallic to a metallic state typically involves changes in electron mobility and the formation of a conduction band, a process that in solids is often associated with defining crystal structure and temperature-dependent properties. However, liquids defy some of these constraints due to their inherent molecular disorder and dynamism. Professor Jungwirth and colleagues have long focused on the peculiar case of alkali metals dissolved in liquid ammonia, a classical system where metallic behavior emerges abruptly as the solution changes color from blue to a lustrous golden hue. This visual transformation heralds the formation of a conduction network from free electrons donated by alkali metal atoms, yet until now, the intermediate stages within this transition have remained elusive.
Central to this new investigation is the application of state-of-the-art molecular dynamics simulations that can faithfully capture the behavior of electrons and ions on ultrafast timescales and at atomic resolution. The simulations reveal a previously overlooked regime where the system does not settle into either the metallic or nonmetallic state but instead exhibits a rapid “flipping” or oscillation between these electronic configurations. This "third phase" defies traditional equilibrium descriptions and compels a reconsideration of the criteria defining phase transitions in conductive liquids. The switching occurs on the scale of tens of femtoseconds (one femtosecond being one quadrillionth of a second), orders of magnitude faster than conventional experimental techniques have been able to probe.
Professor Jungwirth underscores the novelty of this phenomenon: “No one had previously realized that such a system might oscillate so rapidly between these two fundamentally different electronic states. These dynamics had simply not been accounted for in theoretical or experimental frameworks before.” This insight opens new vistas for understanding how conduction emerges and dissolves in disordered environments, potentially impacting fields as diverse as materials science, condensed matter physics, and electrochemistry.
Capturing such rapid transitions experimentally presents a formidable challenge. The temporal resolution required transcends the capabilities of conventional spectroscopy methods. To address this, the IOCB Prague team intends to harness ultrafast laser technology, which can deliver pulses short enough to act as snapshots of these fleeting electronic states. PhD student Marco Vítek, first author of the study, explains, “Our aim is to develop an experimental setup using ultrafast laser pulses that can effectively ‘freeze’ the system’s state at different moments, allowing us to observe these flips directly. Some of these laser sources are already available at our institute, bringing this ambitious goal within reach.”
Collaboration with internationally renowned institutions, including the University of Oxford, the Faculty of Mathematics and Physics at Charles University, and the J. Heyrovský Institute of Physical Chemistry, has been instrumental in pushing the boundaries of computational and experimental prowess required for this research. Together, the teams have employed a combination of high-performance computing and sophisticated quantum mechanical models to achieve unprecedented simulation accuracy.
The implications of this discovery extend beyond merely redefining a classic physical transition. The intermittent, ultrafast switching points to a novel quantum-mechanical process intrinsic to liquids containing dissolved alkali metals. It suggests that conductivity in such systems does not arise from a smooth crossover but rather from a dynamic equilibrium with rapid fluctuations. This challenges the universality of static phase diagrams and compels theorists to incorporate time-dependent variables into models of liquid metals.
If experimentally verified, this phenomenon could have broad technological ramifications. Understanding ultrafast electronic state fluctuations could inform the design of novel materials with tailored conduction properties, potentially impacting energy storage, catalysis, and sensor technologies. Moreover, it may necessitate new interpretations of data gathered from systems where fast electronic processes play a critical role.
The study, published in the prestigious journal Nature Communications, represents a milestone in physical chemistry and condensed matter physics. The research leverages computational simulation/modeling methodologies that capture phenomena inaccessible through classical experimental setups alone. This computational insight, complemented by planned ultrafast spectroscopic experiments, defines a new milestone in the exploration of liquid state physics.
Of particular interest is the methodological framework developed by the team, which integrates electronic structure calculations with molecular dynamics to simulate real-time electron behavior in complex liquid environments. This multiscale modeling offers a blueprint for future studies investigating transient phenomena in other chemical and physical systems.
In summary, the discovery of a rapid flipping behavior between electrolyte and metallic states in ammonia solutions of alkali metals opens a fresh theoretical and experimental frontier. It challenges prevailing dogma, invites a reexamination of the metal-nonmetal transition, and bridges the gulf between chemical physics and ultrafast spectroscopy. This study signals a profound advance in our grasp of the liquid metal state and sets the stage for experimental verification that could rewrite textbooks on physical phase transitions.
Subject of Research: Physical sciences – Chemistry – Chemical physics / Molecular dynamics
Article Title: Rapid flipping between electrolyte and metallic states in ammonia solutions of alkali metals
News Publication Date: 8-May-2025
Web References:
http://dx.doi.org/10.1038/s41467-025-59071-z
References:
Vitek, M.; Igor Rončević; Marsalek, O.; Schewe, H. C.; Jungwirth, P. Rapid Flipping between Electrolyte and Metallic States in Ammonia Solutions of Alkali Metals. Nat. Commun. 2025, 16 (1).
Image Credits:
Photo: Tomáš Belloň/IOCB Prague
Keywords:
Chemical physics, Molecular dynamics
