The A mixed crystal compound [Co(0.8)Fe(0.2)(C16-terpy)(2)](BF(4))(2) (2) (C16-terpy is 4'-hexadecyloxy-2,2':6',2''-terpyridine) with long alkyl chains was prepared by mixing [Co(C16-terpy)(2)](BF(4))(2) (1), which exhibits unique magnetic behavior, and the diamagnetic iron(II) compound [Fe(C16-terpy)(2)](BF(4))(2) (3). The long-lived metastable state in the frozen-in effect was observed for the first time in the spin-crossover cobalt(II) compound 2. Furthermore, relaxation from metastable to stable states was very slow because of a large structural transition resulting from the long alkyl chains.
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http://dx.doi.org/10.1021/ic9015417 | DOI Listing |
Phys Rev Lett
December 2024
Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Distinguishing whether a system supports alternate low-energy (locally stable) states-stable (true vacuum) versus metastable (false vacuum)-by direct observation can be difficult when the lifetime of the state is very long but otherwise unknown. Here we demonstrate, in a tractable model system, that there are physical phenomena on much shorter timescales that can diagnose the difference. Specifically, we study the time evolution of the magnetization following a quench in the tilted quantum Ising model, and show that its magnitude spectrum is an effective diagnostic.
View Article and Find Full Text PDFAdv Sci (Weinh)
December 2024
Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA, 70803, USA.
Phys Rev Lett
September 2024
5. Physikalisches Institut and Center for Integrated Quantum Science and Technology, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
Faraday Discuss
January 2025
School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, Wales, UK.
We present a discussion of the range of NMR techniques that have been utilized for monitoring of crystallization processes, highlighting the opportunities that now exist for exploiting the versatility of NMR techniques to reveal insights into the changes that occur in both the solid phase and the liquid phase as a function of time during crystallization processes from solution. New results are presented from NMR studies of a range of crystallization processes using the CLASSIC NMR strategy and other techniques, specifically covering the following topics: (i) crystallization of glycine from aqueous solution at low temperature, revealing the relatively long-lived existence of a pure phase of the highly meta-stable β polymorph, (ii) the complementarity of H→C cross-polarization NMR and direct-excitation C NMR techniques in probing the evolution of the solid and liquid phases in NMR studies of crystallization processes, (iii) NMR studies of the process of guest exchange between a crystalline host-guest material in contact with the liquid phase of a more favourable type of guest, and (iv) systematic studies of the influence of magic-angle sample spinning on the behaviour of a crystallization system.
View Article and Find Full Text PDFChaos
September 2024
Department of Physics, Boston University, Boston, Massachusetts 02215, USA.
The Fermi-Pasta-Ulam-Tsingou (FPUT) paradox is the phenomenon whereby a one-dimensional chain of oscillators with nonlinear couplings shows long-lived nonergodic behavior prior to thermalization. The trajectory of the system in phase space, with a long-wavelength initial condition, closely follows that of the Toda model over short times, as both systems seem to relax quickly to a non-thermal, metastable state. Over longer times, resonances in the FPUT spectrum drive the system toward equilibrium, away from the Toda trajectory.
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