{"id":520411,"date":"2026-06-09T16:04:16","date_gmt":"2026-06-09T14:04:16","guid":{"rendered":"https:\/\/www.unipi.it\/news\/il-segreto-dei-vetri-svelato-ai-raggi-x-cosi-la-materia-scivola-verso-limmobilita\/"},"modified":"2026-06-16T12:01:32","modified_gmt":"2026-06-16T10:01:32","slug":"the-secret-of-glass-revealed-by-x-rays-how-matter-slides-towards-immobility","status":"publish","type":"news","link":"https:\/\/www.unipi.it\/en\/news\/the-secret-of-glass-revealed-by-x-rays-how-matter-slides-towards-immobility\/","title":{"rendered":"The secret of glass revealed by X-rays: how matter \u201cslides\u201d towards immobility"},"content":{"rendered":"<div class=\"x_elementToProof\" data-olk-copy-source=\"MessageBody\">\n<p>A study conducted at the European Synchrotron Radiation Facility (ESRF<strong>)<\/strong> in Grenoble by researchers from the Universities of Brussels, Padua and Pisa, together with ESRF, and published in <em>Nature Physics<\/em> under the title <em>\u201cAt the Crossover Between Quasi-Localized Dynamics and Diffusion in Deeply Supercooled Liquids\u201d<\/em>, reshapes our understanding of the molecular dynamics that govern the transition of liquids towards the glassy state. The research reveals that the \u201cdance of molecules\u201d is not made up of separate and independent motions, but rather of a single coherent mechanism.<\/p>\n<p>What separates a flowing liquid from a solid, brittle glass? At first glance, the answer seems straightforward: in the former, atoms move freely; in the latter, they are locked in place. Yet for condensed matter physicists, the so-called glass transition remains one of nature\u2019s most challenging puzzles. As a liquid is cooled towards the glassy state, the time required for molecules to reorganise increases exponentially, while their atomic structure remains almost unchanged.<\/p>\n<p>How can a system become rigid without altering the arrangement of its components? For decades, physicists have interpreted this phenomenon as the superposition of different types of motion. On long timescales, there is structural relaxation, the main process through which molecules eventually escape the \u201cmolecular cages\u201d formed by their neighbours, allowing the liquid to flow. At the opposite extreme, on short timescales, are the frenetic vibrations of atoms trapped within those same cages.<\/p>\n<p>Between these two extremes lies the mysterious Johari\u2013Goldstein relaxation, first identified in the 1970s. For fifty years, scientists have debated whether it represents an autonomous local motion or whether it is instead connected to the liquid\u2019s main relaxation process.<\/p>\n<p>\u201cJohari\u2013Goldstein relaxation plays a crucial role in glasses because it is responsible for their residual mobility,\u201d <strong>explains Giulio Monaco of the Department of Physics and Astronomy at the University of Padua<\/strong>. \u201cIt is linked to important but hard-to-predict properties such as ductility and resistance to crystallisation. Until now, its microscopic origin remained poorly understood.\u201d<\/p>\n<p>Today, this international research team has used the ESRF\u2019s advanced facilities to investigate this long-standing mystery. The researchers employed a state-of-the-art technique known as X-ray time-domain interferometry, which made it possible both to observe molecular motion at the atomic scale within a time window ranging from 10 nanoseconds to 10 microseconds \u2014 previously almost inaccessible \u2014 and to isolate the signature of Johari\u2013Goldstein relaxation.<\/p>\n<p>\u201cOur experiment provides information about Johari\u2013Goldstein relaxation in reciprocal space, and this information must then be transformed into real space,\u201d <strong>explains Federico Caporaletti of the Experimental Soft Matter and Thermal Physics group at the Universit\u00e9 libre de Bruxelles<\/strong>. \u201cThe image of this relaxation in real space became progressively clearer as more information became available in reciprocal space, until, at a certain point, everything fell into place.\u201d<\/p>\n<p>The results, published in <em>Nature Physics<\/em>, overturn previous assumptions: beta relaxation is not an isolated and independent event. Instead, it is the direct precursor of structural relaxation \u2014 the first sign of the breakdown of molecular cages that ultimately leads to the material becoming fluid.<\/p>\n<p>Although the study does not invalidate previous models, it suggests that the distinction between different types of relaxation may be more formal than substantial. At the microscopic level, the dynamics are deeply interconnected.<\/p>\n<p>\u201cAfter almost ten years of research in our laboratories and at ESRF\u2019s ID18 beamline, we have finally understood the microscopic origin of some very important properties of glasses,\u201d <strong>concludes Simone Capaccioli of the Department of Physics at the University of Pisa<\/strong>. \u201cThese results could contribute to the design of glasses with properties better tailored to society\u2019s needs.\u201d<\/p>\n<p><strong>\u00a0<\/strong><\/p>\n<p><strong>Research link<\/strong>: <a href=\"https:\/\/www.nature.com\/articles\/s41567-026-03320-5\">https:\/\/www.nature.com\/articles\/s41567-026-03320-5<\/a><\/p>\n<p><strong>Title:<\/strong> <em>At the Crossover Between Quasi-Localized Dynamics and Diffusion in Deeply Supercooled Liquids<\/em> (<em>Nature Physics<\/em>, 2026)<\/p>\n<p><strong>Authors:<\/strong> Federico Caporaletti, Simone Capaccioli, Dimitrios Bessas, Aleksandr I. Chumakov, Alessandro Martinelli, Francesco Dallari and Giulio Monaco.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>The study, conducted by the Universities of Brussels, Padua, Pisa and ESRF and published in Nature Physics, reveals new insights into the behaviour of supercooled liquids<\/p>\n","protected":false},"featured_media":519851,"menu_order":3,"template":"","format":"standard","meta":[],"tag-notizie-persone":[],"tags_news":[1222,2305],"categorie":[159],"class_list":["post-520411","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","tags_news-department-of-physics","tags_news-research-en","categorie-unipinews-en"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>The secret of glass revealed by X-rays: how matter \u201cslides\u201d towards immobility ~ UNIPI<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, 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