Dynamics & Spectroscopy with Neutrons—Recent Developments & Emerging Opportunities

Abstract

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.

Spectroscopic Signatures of Hydrogen-Bonding Motifs in Protonic Ionic Liquid Systems: Insights from Diethylammonium Nitrate in the Solid State

“…A very good reproduction of the antisymmetric stretching band by AIMD (ν­[NH 2 ] = ca. 2850 cm –1 ) using an effective temperature of 350 K signals the importance of nuclear quantum effects (NQEs) and associated zero-point energies, which are not included in the classical simulations from the outset, and are expected to further drag the predicted band position to lower energies if accounted for explicitly in the simulations. , The presented analysis also rules out the propensity of the ν­[N–H] stretch vibration to drive proton migration in the low-temperature phase of DEAN, which would not be accessible at room temperature. Consequently, and of relevance to the interpretation of the experimental spectra, these findings do not support the coexistence of nitric acid and ethylamine in the crystal lattice of DEAN.…”

Along the road to crystal structure prediction (CSP) of pharmaceutical-like molecules

“…Yet, recent progress in the development of more theoretically justified and computationally efficient solid-state DFT approximations should be noted, with the strongly constrained and appropriately normed (SCAN) 89,90 density functional approximation given as a prime example (see ref. 91 for remarks on its performance). Recently introduced numerically stable and vdW-corrected incarnations of SCAN, i.e.…”

“…104 In the case of GGA-type density functional approximations, there is a well-known lucky compensation of errors due to anharmonicity, resulting in an excellent match to experimental data without any semi-empirical scaling. 91,108–110…”

The Unlocking of High-Pressure Science with Broadband Neutron Spectroscopy at the ISIS Pulsed Neutron & Muon Source

“…Its chief benefits are its highly penetrating nature, the absence of hard spectroscopic selection rules, and a very high incoherent neutron-scattering cross-section for the proton, providing extreme sensitivity to motions involving hydrogen atoms. In addition, the past decade has witnessed a very rapid increase in the quantity and quality of combined in-silico and INS studies, giving unprecedented clarity to a range of chemical phenomena at the atomic scale [4,5,6]. Some examples include the understanding of phase transitions [7,8,9], quantifying the role of vibrations to the kinetics in catalytic processes [10] and gas absorption in porous media [11].…”