%0 Book Section %1 statphys23_0661 %A Timan, T. Zykova %A Ceresoli, D. %A Tartaglino, U. %A Tosatti, E. %B Abstract Book of the XXIII IUPAP International Conference on Statistical Physics %C Genova, Italy %D 2007 %E Pietronero, Luciano %E Loreto, Vittorio %E Zapperi, Stefano %K alkali energies free halides interface nanofriction nomelting partial statphys23 surface topic-6 wetting %T Physics and Nanofriction of NaCl Surfaces near the Melting Point %U http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=661 %X The high temperature surface properties of alkali halides are very unusual, as the crystal surfaces are incompletely wetted by their own melt. Classical molecular dynamics simulations based on the Tosi-Fumi potential provide a unique opportunity, where all surface properties of this model system can be calculated and intimately understood. We found that crystalline NaCl(100) is nonmelting, and remains in this model stable and free of precursor signals of melting up to the bulk melting point $T_m$, where a simulated droplet of melt indeed shows partial wetting. Building on simulations, we calculated the solid-vapor, liquid-vapor, and solid-liquid interface free energies as a function of temperature. Analysis of these results shows that the anomalous wetting properties of NaCl(100) eventually stem from three reasons: (i) the solid surface is enormously anharmonic, with a very low free energy; (ii) the solid-liquid interface is instead relatively costly, on account of a very large density difference; (iii) the liquid surface free energy is finally surprisingly high, despite an apparent lack of local crystal-like order. Calculations reveal a liquid surface entropy deficit, whose reason is traced to short range incipient molecular order.1 Its extreme nonwetting properties may make crystalline NaCl(100) an ideal substrate for studies of high temperature sliding nanofriction by hard tips. We conducted direct nanofriction simulations both in the heavy ploughing, wear-dominated regime, and in the light grazing, wearless friction regime. Plowing friction is found to drop close to melting (as in ice skating). Grazing friction peaks instead close to melting, where linear response shows the solid surface compliance to surge.2 References\\ 1) T. Zykova-Timan, D. Ceresoli, U. Tartaglino, E. Tosatti, Phys. Rev.Lett. 94, 176105 (2005); J. Chem. Phys. 123, 164701 (2005).\\ 2) T. Zykova-Timan, D. Ceresoli, E. Tosatti, Nature Materials 6, 231 (2007).

@incollection{statphys23_0661, abstract = {The high temperature surface properties of alkali halides are very unusual, as the crystal surfaces are incompletely wetted by their own melt. Classical molecular dynamics simulations based on the Tosi-Fumi potential provide a unique opportunity, where all surface properties of this model system can be calculated and intimately understood. We found that crystalline NaCl(100) is nonmelting, and remains in this model stable and free of precursor signals of melting up to the bulk melting point $T_m$, where a simulated droplet of melt indeed shows partial wetting. Building on simulations, we calculated the solid-vapor, liquid-vapor, and solid-liquid interface free energies as a function of temperature. Analysis of these results shows that the anomalous wetting properties of NaCl(100) eventually stem from three reasons: (i) the solid surface is enormously anharmonic, with a very low free energy; (ii) the solid-liquid interface is instead relatively costly, on account of a very large density difference; (iii) the liquid surface free energy is finally surprisingly high, despite an apparent lack of local crystal-like order. Calculations reveal a liquid surface entropy deficit, whose reason is traced to short range incipient molecular order.[1] Its extreme nonwetting properties may make crystalline NaCl(100) an ideal substrate for studies of high temperature sliding nanofriction by hard tips. We conducted direct nanofriction simulations both in the heavy ploughing, wear-dominated regime, and in the light grazing, wearless friction regime. Plowing friction is found to drop close to melting (as in ice skating). Grazing friction peaks instead close to melting, where linear response shows the solid surface compliance to surge.[2] References\\ 1) T. Zykova-Timan, D. Ceresoli, U. Tartaglino, E. Tosatti, Phys. Rev.Lett. 94, 176105 (2005); J. Chem. Phys. 123, 164701 (2005).\\ 2) T. Zykova-Timan, D. Ceresoli, E. Tosatti, Nature Materials 6, 231 (2007).}, added-at = {2007-06-20T10:16:09.000+0200}, address = {Genova, Italy}, author = {Timan, T. Zykova and Ceresoli, D. and Tartaglino, U. and Tosatti, E.}, biburl = {https://www.bibsonomy.org/bibtex/2862e09b2c037c40453b6fcb15a43ea82/statphys23}, booktitle = {Abstract Book of the XXIII IUPAP International Conference on Statistical Physics}, editor = {Pietronero, Luciano and Loreto, Vittorio and Zapperi, Stefano}, interhash = {d3ef72b3d07e044172a110a6d42a3028}, intrahash = {862e09b2c037c40453b6fcb15a43ea82}, keywords = {alkali energies free halides interface nanofriction nomelting partial statphys23 surface topic-6 wetting}, month = {9-13 July}, timestamp = {2007-06-20T10:16:26.000+0200}, title = {Physics and Nanofriction of NaCl Surfaces near the Melting Point}, url = {http://st23.statphys23.org/webservices/abstract/preview_pop.php?ID_PAPER=661}, year = 2007 }