Hydrogen bond dynamics in sodium hydrogen bissulfate.

Detailed research on the nature of hydrogen bond (HB), including the examination of the influence of the environment, e.g., crystal field, on the structure and dynamics, is of prime importance for the understanding of proton conductivity and is vital for the design of new and improved materials with desired properties. A precise description of proton dynamics is essential for accurate characterisation and prediction of properties of H-bonded ferroelectrics. Crystalline sodium hydrogen bissulfate (SHBS) is a ferroelectric system with the shortest non-symmetric HB known in the literature. As the shapes of both incident neutron energy-dependent transmission (NT) and NCS peaks on Vesuvio depend on the atom-projected VDOSes and, thus, on the underlying PMFs, we propose to employ both techniques to investigate the local nuclear quantum dynamics of SHBS and its deuterated counterpart systems at 10K, 100K, 200K, 300K and 550K. In addition to the VESUVIO proposal, SXD and TOSCA proposals will be submitted. From the SXD data on a single crystal of the SHBS and its deuterated counterpart, the average and local structure (in terms of the thermal ellipsoids) will be established. TOSCA data will serve as a comparison with the ab initio computed O–H (O-D) stretching envelope. The use of isotopologues will enable us to perform a critical appraisal of isotope effects on the local structure and dynamics.