H/D isotope effect on the molar volume and thermal expansion of benzene

Abstract

Time-of-flight neutron powder diffraction data have been collected from C₆H₆ and C₆D₆, as a function of temperature between 10 and 276 K using the High Resolution Powder Diffractometer at the ISIS Neutron and Muon Source. In order to achieve high accuracy and precision both in the determination of lattice parameters and in the control of the sample temperature, data were acquired using the same instrumental conditions for each isotopologue with an internal NIST silicon standard and in situ-heated sample holders. In contrast with the work from J. D. Dunitz and R. M. Ibberson, Angew. Chem. Int. Ed., 2008, 47, 4208–4210, we find that the difference in molar volume between the two isotopologues is almost invariant with temperature and that the anisotropic linear expansivities of the crystallographic axes are nearly identical in C₆H₆ and C₆D₆.