Colloqui di Fisica: Nuclear quantum effects in condensed matter
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Martedì 4 febbraio 2025 alle ore 14:30, il prof. Fabio Finocchi dell'Institut des NanoSciences de Paris (INSP), CNRS and Sorbonne University, terrà il Colloquio di Fisica dal titolo "Nuclear quantum effects in condensed matter"
Abstract: It becomes nowadays possible to conceive and design materials with specific properties, almost from scratch. Matter consists of an assembly of electrons and nuclei. Although much heavier than electrons, light nuclei, mainly hydrogen, exhibit quantization of the vibrational levels, zero-point energy and tunnelling. These so-called Nuclear Quantum Effects (NQE) can have a large impact on the structure and the dynamics of materials [1]. NQE are also crucial for describing heavier nuclei at low temperatures and other phenomena, such as isotope effects, that escape a purely classical frame. The behaviour of systems that are at the borderline between the classical and quantum worlds is in general complex [4]. The genuine quantum characteristics might be spoiled by electric fields, high disorder, etc. I will illustrate through selected examples some paradoxical effects that can be encountered in condensed matter : ice [5,6] and exotic phases of methane hydrates [7,8] at extreme pressures, typical of those inside giant icy planets of the solar system. I will also show the spectacular isotope effects in the phase transition of Sodium Hydroxide, which has hindered its explanation for about 40 years [9]. I will conclude by discussing the importance of simulation methods that are able to account for the quantum dynamics of nuclei. In the last decade, in our group we have developed numerical models and theories that account for nuclear quantum effects, at various approximation levels [2,3,4]. for instance in the semi-classical regime [2,3], in the framework of the generalized Langevin equation. The advent of machine-learning based techniques has opened the way to refine models for describing the inter-atomic forces, and the nuclear quantum effects, even if modest, might change the statistical properties appreciably. Their explicit inclusion in simulations is an emerging field of research, with impact on many fields, spanning materials science, geophysics, physical chemistry and biochemistry.
Aula A - Via della Vasca Navale 84 (primo piano)
[1] T. Markland, M. Ceriotti, Nuclear quantum effects enter the mainstream, Nature Rev. Chem. 2 (2018) 0109. [2] E. Mangaud et al., “The fluctuation–dissipation theorem as a diagnosis and cure for zero-point energy leakage in quantum thermal bath simulations”, J. Chem. Theory Comput. 15 (2019) 2863. [3] S Huppert, T Plé, S Bonella, P Depondt, F Finocchi, “Simulation of nuclear quantum effects in condensed matter via quantum baths”, Appl. Sci. 12 (2022) 4756. [4] Thomas Plé et al. “Anharmonic spectral features via trajectory-based quantum dynamics: a perturbative analysis of the interplay between dynamics and sampling”, J. Chem. Phys. 155 (2021) 22328. [5] Y. Bronstein, P. Depondt, F. Finocchi, and A. M. Saitta, “Quantum-driven phase transition in ice described via an efficient Langevin approach”, Phys. Rev. B 89 (2014), 214101. [6] Y. Bronstein et al., “Quantum versus classical protons in pure and salty ice under pressure”, Phys. Rev. B 93 (2016), 024104. [7] S. Schaack et al., Observation of methane filled hexagonal ice stable up to 150 GPa, Proc. Natl. Acad. Sci. 116 (2019) 16204. [8] S. Schaack, P. Depondt, M. Moog, F. Pietrucci, and F. Finocchi, How methane hydrate recovers at very high pressure the hexagonal ice structure, J. Chem. Phys. 152 (2020), 024504. [9] S Schaack et al. “When quantum fluctuations meet structural instabilities: the isotope- and pressure-induced phase transition in the quantum paraelectric NaOH”, Phys. Rev. Lett. 131 (2023) 126101. (All publications are freely available on HAL)
