Vibrational properties of water retained in graphene oxide

Vibrational properties of water molecules retained in the interlayer space of graphene oxide were studied by combining inelastic neutron scattering spectroscopy with density functional theory calculations. The credibility of Lerf–Klinowski model in the description of the amplitude weighted vibrational density of states has been successfully examined. The solid-state plane-wave DFT computations have delivered sat- isfying qualitative interpretation of the INS spectrum, which was found to be mainly driven by the vibra- tional dynamics of the retained water

Dynamics and Spectroscopy with Neutrons—Recent Developments and Emerging Opportunities

This work provides an up-to-date overview of recent developments in neutron spectroscopic techniques and associated computational tools to interrogate the structural properties and dynamical behavior of complex and disordered materials, with a focus on those of a soft and polymeric nature. These have and continue to pave the way for new scientific opportunities simply thought unthinkable not so long ago, and have particularly benefited from advances in high-resolution, broadband techniques spanning energy transfers from the meV to the eV. Topical areas include the identification and robust assignment of low-energy modes underpinning functionality in soft solids and supramolecular frameworks, or the quantification in the laboratory of hitherto unexplored nuclear quantum effects dictating thermodynamic properties. In addition to novel classes of materials, we also discuss recent discoveries around water and its phase diagram, which continue to surprise us. All throughout, emphasis is placed on linking these ongoing and exciting experimental and computational developments to specific scientific questions in the context of the discovery of new materials for sustainable technologies.This research was funded by the Gipuzkoako Foru Aldundia under Grant Number 2020-CIEN-000009-01

Unravelling the Ordered Phase of the Quintessential Hybrid Perovskite MAPbI3 – Thermophysics to the Rescue

Hybrid organic-inorganic perovskites continue to attract an enormous amount of attention, yet a robust microscopic picture of their different phases as well as the extent and nature of the disorder present remain elusive. Using specific-heat data along with high-resolution inelastic neutron scattering and ab initio modeling, we address this ongoing challenge for the case of the ordered phase of the quintessential hybrid perovskite MAPbI3. At low-temperatures, the specific heat of MAPbI3 reveals strong deviations from the Debye limit, a common feature of pure hybrid perovskites and their mixtures. We find that these deviations are exquisitely sensitive to the underlying low-energy phonon band structure, thus paving the way for a quantitative and robust assessment of available structural models beyond what has been possible to date. Our thermophysical analysis demonstrates that the (otherwise ordered) structure around the organic moiety is characterized by a substantial lowering of the local symmetry relative to what can be inferred from crystallographic studies. The ab initio phonon calculations also provide a means of exploring in detail the physical origin of the observed thermophysical anomalies, which can now be unequivocally associated with excitations of sub-Terahertz optical phonons responsible for translational and librational distortions of the octahedral units. To the best of our knowledge, this is the first time that such a model-selection protocol using thermophysical properties as key input has been deployed with success in the study of this important class of materials