Classical infrared spectra of ionic crystals and their relevance for statistical mechanics
| Autor: | Alberto Maiocchi, Luigi Galgani, Andrea Carati, Fabrizio Gangemi, Roberto Gangemi |
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| Přispěvatelé: | Carati, A, Galgani, L, Maiocchi, A, Gangemi, F, Gangemi, R |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Statistics and Probability
Work (thermodynamics) Ionic crystal model Infrared spectroscopy FOS: Physical sciences Kinetic energy 01 natural sciences Spectral line Thermal expansion 010305 fluids & plasmas Crystal 0103 physical sciences Statistical physics 010306 general physics Equipartition theorem Condensed Matter - Statistical Mechanics Physics Infrared spectra Equipartition principle Ordered and chaotic motions FPU model Statistical Mechanics (cond-mat.stat-mech) Statistical mechanics Condensed Matter Physics Optics (physics.optics) Physics - Optics |
| Popis: | It was recently shown that the experimental infrared spectra of ionic crystals at room temperature are very well reproduced by classical realistic models, and here new results are reported on the temperature dependence of the spectra, for the LiF crystal. The principal aim of the present work is however to highlight the deep analogy existing between the problem of spectra in ionic crystal models on the one hand, and that of energy equipartition in the Fermi--Pasta--Ulam model, on the other. Indeed at low temperatures the computations of the spectra show that the dynamics of the considered system is not completely chaotic, so that the use of the Boltzmann--Gibbs statistics is put in question, as in the Fermi--Pasta--Ulam case. Here, however, at variance with the equipartition problem, a first positive indication is given on the modifications that should be introduced in a classical statistical treatment: the new results at low temperatures show that it is indeed the Clausius identification of temperature that has to be modified. In fact, at very low temperatures the theoretical spectra fail to reproduce the experimental ones, if the temperature is taken as proportional to mean kinetic energy, but agreement is recovered through the only expedient of introducing a suitable temperature rescaling. Analogous results are also found in connection with thermal expansion. Sent for publication in Physica A |
| Databáze: | OpenAIRE |
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