The Repulsive Force Between Atoms: A Quantum Explanation

Author: Denis Avetisyan

New theoretical work reveals a previously overlooked repulsive interaction between neutral atoms arising from the interplay of light and collective electronic excitations.

The analysis details error inherent in approximating $ \mathcal{I}\_{\rm appr}(\bar{k};\gamma,\tau,\eta)$, suggesting that any such approximation will inevitably carry a quantifiable degree of deviation dependent on parameters $\gamma$, $\tau$, and $\eta$.

Combining many-body quantum electrodynamics with the quantum Drude oscillator model unveils a repulsive, inverse-distance potential significant at intermediate and short ranges.

Conventional wisdom dictates that interatomic forces either fall off rapidly with distance or are attractive, yet this work, titled ‘Repulsive Inverse-Distance Interatomic Interaction from Many-Body Quantum Electrodynamics’, reveals a persistent, repulsive interaction scaling as the inverse distance between neutral atoms. Through perturbative many-body quantum electrodynamics—modeling atoms as coupled quantum Drude oscillators—we demonstrate this arises from coupling between virtual photons and molecular plasmons in the non-retarded regime. Though weaker than van der Waals forces, could this repulsive interaction become dominant in regimes where gravity is negligible, potentially influencing experiments probing quantum gravity at microscopic scales?

The Illusion of Pairwise Sums

Traditional models of intermolecular interaction simplify reality by treating each interaction as a sum of pairwise contributions. This neglects the crucial influence of collective effects arising from simultaneous interactions, leading to inaccuracies in predicting material properties. A key limitation is the inadequate treatment of many-body dispersion (MBD), which describes correlated electron motion and long-range interactions vital in systems like van der Waals materials. Realistic modeling requires a framework that captures these collective electronic responses—acknowledging that interactions aren’t isolated, but emergent phenomena.

The Electromagnetic Field: A Precise, Yet Limited, Description

Quantum Electrodynamics (QED) precisely describes the interaction of light and matter through the electromagnetic field. Its success is evidenced by accurate predictions like the anomalous magnetic moment of the electron. The minimal coupling term within QED elegantly describes this interaction, allowing for probability calculations through perturbation theory. However, applying perturbative QED to complex many-body systems becomes computationally intractable due to the factorial growth of required diagrams, necessitating a more scalable approach.

Many-Body QED: Growing a Collective Description

Many-Body Quantum Electrodynamics (MB-QED) extends perturbative QED and many-body theory, accurately describing interactions in complex systems. A core component is the Quantum Drude Oscillator (QDO) model, which characterizes the electronic response of matter through coupled dipole moments and their interactions. MB-QED captures crucial screening and correlation effects, revealing an inverse-distance interaction—a repulsive force contributing up to 10% of total dispersion energy and influencing material stability.

Predicting Failure, Designing for the Inevitable

Many-body quantum electrodynamics (MB-QED) advances our ability to model collective electron behavior, accurately accounting for complex interactions between electrons and photons. This enables more precise predictions of material properties and opens avenues for designing materials with tailored functionalities – from high-strength alloys to advanced catalysts. Furthermore, MB-QED’s connection to the quantum vacuum predicts measurable forces within the zepto-Newton range, accessible to current measurements. Stability, it seems, is merely the prelude to a more interesting rearrangement.

The pursuit of fundamental forces reveals a curious tendency: attempts to define interaction often unearth unexpected repulsion. This work, detailing a repulsive inverse-distance interaction between atoms stemming from coupled molecular plasmons and virtual photons, exemplifies this beautifully. It suggests that even neutrality doesn’t preclude a fundamental aversion at short ranges. As John Bell once observed, “No physical theory can be considered complete unless it accounts for all possible correlations.” This framework, building upon many-body quantum electrodynamics, demonstrates a correlation previously obscured – a subtle, yet significant, repulsion that challenges simplistic models of atomic interaction and reminds one that scalability is often just the word used to justify complexity. The perfect architecture, in this case a complete understanding of even seemingly simple interactions, remains elusive, a myth to keep us sane.

The Horizon Beckons

This work, revealing a repulsive contribution to the van der Waals family, does not so much solve a problem as relocate it. The comfortable narrative of purely attractive, distance-dependent forces now bears a ghost – a subtle, yet potentially critical, counterpoint. It is a reminder that every refinement of a model merely exposes the next layer of complexity, the inevitable failure case lurking just beyond the current precision. The theoretical edifice, painstakingly constructed, finds itself balanced on a new, previously unseen fulcrum.

The immediate challenge lies not in proving this repulsion—given enough parameters, any story can be told—but in demonstrating its measurable impact amidst the cacophony of other, stronger interactions. One anticipates a proliferation of simulations, each attempting to isolate and amplify this signal, until the model itself becomes the dominant noise. The true test will be in systems far from equilibrium, where these subtle balances are disrupted and the repulsive force might dictate emergent behavior.

Ultimately, this investigation shifts the focus from forces as isolated phenomena, to the collective behavior of fluctuating electromagnetic fields. It whispers that order—the neat, predictable attraction—is merely a temporary cache between failures, a local minimum in a vast, chaotic landscape. The future likely holds not a unified theory of intermolecular forces, but a deeper understanding of the self-organizing principles governing their delicate, transient dance.

Original article: https://arxiv.org/pdf/2511.08069.pdf

Contact the author: https://www.linkedin.com/in/avetisyan/

The Illusion of Pairwise Sums

The Electromagnetic Field: A Precise, Yet Limited, Description

Many-Body QED: Growing a Collective Description

Predicting Failure, Designing for the Inevitable

The Horizon Beckons

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