Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations
A second melting temperature occurs at a temperature T<sub>n+</sub> higher than T<sub>m</sub> in glass-forming melts after heating them from their glassy state. The melting entropy is reduced or increased depending on the thermal history and on the presence of antibonds or bo...
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| Online Access: | https://www.mdpi.com/1996-1944/14/21/6509 |
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| author | Robert F. Tournier Michael I. Ojovan |
| author_facet | Robert F. Tournier Michael I. Ojovan |
| author_sort | Robert F. Tournier |
| collection | DOAJ |
| description | A second melting temperature occurs at a temperature T<sub>n+</sub> higher than T<sub>m</sub> in glass-forming melts after heating them from their glassy state. The melting entropy is reduced or increased depending on the thermal history and on the presence of antibonds or bonds up to T<sub>n+</sub>. Recent MD simulations show full melting at T<sub>n+</sub> = 1.119T<sub>m</sub> for Zr, 1.126T<sub>m</sub> for Ag, 1.219T<sub>m</sub> for Fe and 1.354T<sub>m</sub> for Cu. The non-classical homogeneous nucleation model applied to liquid elements is based on the increase of the Lindemann coefficient with the heating rate. The glass transition at T<sub>g</sub> and the nucleation temperatures T<sub>nG</sub> of glacial phases are successfully predicted below and above T<sub>m</sub>. The glass transition temperature T<sub>g</sub> increases with the heating rate up to T<sub>n+</sub>. Melting and crystallization of glacial phases occur with entropy and enthalpy reductions. A universal law relating T<sub>n+</sub> and T<sub>nG</sub> around T<sub>m</sub> shows that T<sub>nG</sub> cannot be higher than 1.293T<sub>m</sub> for T<sub>n+</sub>= 1.47T<sub>m</sub>. The enthalpies and entropies of glacial phases have singular values, corresponding to the increase of percolation thresholds with T<sub>g</sub> and T<sub>nG</sub> above the Scher and Zallen invariant at various heating and cooling rates. The G-phases are metastable up to T<sub>n+</sub> because the antibonds are broken by homogeneous nucleation of bonds. |
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| spelling | doaj.art-36ff50ba67b041c4b09f5964a22eb8bb2023-11-22T21:13:13ZengMDPI AGMaterials1996-19442021-10-011421650910.3390/ma14216509Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics SimulationsRobert F. Tournier0Michael I. Ojovan1UPR 3228 Centre National de la Recherche Scientifique, Laboratoire National des Champs Magnétiques Intenses, European Magnetic Field Laboratory, Institut National des Sciences Appliquées de Toulouse, Université Grenoble Alpes, F-31400 Toulouse, FranceDepartment of Materials, Imperial College London, London SW7 2AZ, UKA second melting temperature occurs at a temperature T<sub>n+</sub> higher than T<sub>m</sub> in glass-forming melts after heating them from their glassy state. The melting entropy is reduced or increased depending on the thermal history and on the presence of antibonds or bonds up to T<sub>n+</sub>. Recent MD simulations show full melting at T<sub>n+</sub> = 1.119T<sub>m</sub> for Zr, 1.126T<sub>m</sub> for Ag, 1.219T<sub>m</sub> for Fe and 1.354T<sub>m</sub> for Cu. The non-classical homogeneous nucleation model applied to liquid elements is based on the increase of the Lindemann coefficient with the heating rate. The glass transition at T<sub>g</sub> and the nucleation temperatures T<sub>nG</sub> of glacial phases are successfully predicted below and above T<sub>m</sub>. The glass transition temperature T<sub>g</sub> increases with the heating rate up to T<sub>n+</sub>. Melting and crystallization of glacial phases occur with entropy and enthalpy reductions. A universal law relating T<sub>n+</sub> and T<sub>nG</sub> around T<sub>m</sub> shows that T<sub>nG</sub> cannot be higher than 1.293T<sub>m</sub> for T<sub>n+</sub>= 1.47T<sub>m</sub>. The enthalpies and entropies of glacial phases have singular values, corresponding to the increase of percolation thresholds with T<sub>g</sub> and T<sub>nG</sub> above the Scher and Zallen invariant at various heating and cooling rates. The G-phases are metastable up to T<sub>n+</sub> because the antibonds are broken by homogeneous nucleation of bonds.https://www.mdpi.com/1996-1944/14/21/6509melting enthalpy and entropysecond melting temperaturemelting entropy reductioncrystallization enthalpy reductionundercoolingoverheating |
| spellingShingle | Robert F. Tournier Michael I. Ojovan Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations Materials melting enthalpy and entropy second melting temperature melting entropy reduction crystallization enthalpy reduction undercooling overheating |
| title | Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations |
| title_full | Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations |
| title_fullStr | Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations |
| title_full_unstemmed | Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations |
| title_short | Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations |
| title_sort | prediction of second melting temperatures already observed in pure elements by molecular dynamics simulations |
| topic | melting enthalpy and entropy second melting temperature melting entropy reduction crystallization enthalpy reduction undercooling overheating |
| url | https://www.mdpi.com/1996-1944/14/21/6509 |
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