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(317) Production(s) de KOB W.
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Influence of the alkali modifier on the surface properties of silicate glasses 
Auteur(s): Zhang Z., Ispas S., Kob W.
Conference: DGG-USTV JOINT ANNUAL MEETING (Orléans, FR, 2023-05-22)
Ref HAL: hal-04859718_v1
Exporter : BibTex | endNote
Résumé: We have used large-scale molecular dynamics simulations in order to investigate the surface properties of lithium, sodium, and potassium silicate glasses containing 25 mol% of alkali oxide. We have studied two types of surfaces, a melt-formed surface (MS) and a fracture surface (FS), and we have found that the influence of the alkali modifier on the surface properties depends strongly on the nature of the surface. The MS show a saturation of elemental concentration when the alkali is changed from Na to K, while the FS exhibit a monotonic increase of modifier concentration with increasing the alkali size. For the FS we find that larger alkali ions reduce the concentration of under-coordinated Si atoms at the surface and increases the fraction of two-membered rings.For both types of surfaces, the surface roughness of the surfaces are found to increase with alkali size, with the effect being more pronounced for the FS than for the MS. The height-height correlation function of the surfaces show a scaling behavior that is independent of the alkali species considered: The one for the MS is compatible with the prediction of thefrozen capillary wave theory while the ones for the FS shows a logarithmic growth, i.e., on the nanoscale these surfaces are not self-affine fractals. The influence of the modifier on the surface properties are rationalized in terms of the interplay between multiple factors involving the size of the ions, bond strength, and charge balance on the surface.
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Intermediate-range order governs dynamics in dense colloidal liquids
Auteur(s): Singh Navneet, Zhang Z., Sood A.k., Kob W. , Ganapathy Rajesh
(Article) Publié:
Proceedings Of The National Academy Of Sciences Of The United States Of America, vol. 120 p.e2300923120 (2023)
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The medium-range order in silicate glass-formers: From standard two-body indicators to many-body correlations
Auteur(s): Kob W.
Conférence invité: ICG Annual Meeting 2023 (Hangzhou, CN, 2023-11-12)
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Topology of vibrational modes predicts plastic events in glasses
Auteur(s): Wu Zhenwei, Chen Yixiao, Wang Wei-hua, Kob W., Xu Limei
(Article) Publié:
Nature Communications, vol. 14 p.2955 (2023)
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The two faces of friction in the relaxation dynamics of granular systems
Auteur(s): Kob W.
Conférence invité: Komaba Mini-Workshop (Tokyo, JP, 2023-08-22)
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Granular materials under cyclic shear: No elastic regime and they always flow
Auteur(s): Kob W.
Conférence invité: 9th International Discussion Meeting on Relaxation in Complex Systems (Chiba, JP, 2023-08-12)
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Surface properties of alkali silicate glasses: Influence of the modifiers
Auteur(s): Zhang Z., Ispas S., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 158 p.244504 (2023)
Texte intégral en Openaccess : 
Ref HAL: hal-04856797_v1
Ref Arxiv: 2205.02461
DOI: 10.1063/5.0155497
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Using large-scale molecular dynamics simulations, we investigate the surface properties of lithium, sodium, and potassium silicate glasses containing 25 mol % of alkali oxide. The comparison of two types of surfaces, a melt-formed surface (MS) and a fracture surface (FS), demonstrates that the influence of the alkali modifier on the surface properties depends strongly on the nature of the surface. The FS exhibits a monotonic increase of modifier concentration with increasing alkali size while the MS shows a saturation of alkali concentration when going from Na to K glasses, indicating the presence of competing mechanisms that influence the properties of a MS. For the FS, we find that larger alkali ions reduce the concentration of under-coordinated Si atoms and increase the fraction of two-membered rings, implying an enhanced chemical reactivity of the surface. For both types of surfaces, the roughness is found to increase with alkali size, with the effect being more pronounced for the FS than for the MS. The height–height correlation functions of the surfaces show a scaling behavior that is independent of the alkali species considered: The ones for the MS are compatible with the prediction of the frozen capillary wave theory while the ones for the FS show a logarithmic growth, i.e., on the nanoscale these surfaces are not self-affine fractals. The influence of the modifier on the surface properties are rationalized in terms of the interplay between multiple factors involving the size of the ions, bond strength, and charge balance on the surface.
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