Crystallography of hydrogen-containing compounds: realizing the potential of neutron powder diffraction

Abstract

Hydrogen forms more compounds than any other element in the Periodic Table, yet methods for accurately, precisely and rapidly determining its position in a crystal structure are not readily available. The latest generation of high-flux neutron powder diffractometers, operating under optimised collection geometries, allow hydrogen positions to be extracted from the diffraction patterns of polycrystalline hydrogenous compounds without resorting to isotopic substitution. Neutron powder diffraction for hydrogenous materials has a wide range of applications within chemistry. These include the study of hydrogen-energy materials, coordination and organometallic compounds, hydrogen-bonded structures and ferroelectrics, geomaterials, zeolites and small molecule organics, such as simple sugars and amino acids. The technique is particularly well suited to parametric studies, for example as a function of temperature or pressure, where changes in hydrogen bonding patterns or decompositions involving hydrogen-containing molecules, such as water, are monitored.