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Why liquids differ so much is not known.","posed_since":"","precise":"The kinetic fragility $m = d log10(\\tau_{\\alpha}) / d(T_{g}/T)$ evaluated at $T = T_g$ ranges from about 20 for $\\mathrm{SiO_2}$ to above 150 for some polymers. Identify the microscopic determinants of $m$ (softness of the repulsion, network connectivity, vibrational anharmonicity, the heat-capacity jump $\\Delta C_p$ at $T_g$) and give a predictive relation for $m$ tested across a set of chemically different liquids.","problem_ref":"169f0b6faa7371dd3302978930e1cf39753a62e4d7ee2fc66902aa52c5751135","references":"","settled_by":"A relation predicting m from microscopic or thermodynamic inputs that holds within experimental error across a large database of molecular, network, polymeric and metallic glass formers.","status_note":"","title":"What sets the fragility of a glass-forming 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