THE STRUCTURE AND DYNAMICS OF SOLID BENZENE .1. A NEUTRON POWDER DIFFRACTION STUDY OF DEUTERATED BENZENE FROM 4 K TO THE MELTING-POINT

The crystal structure of deuterated benzene has been investigated over the complete temperature range 4-280 K. Our results are in excellent agreement with previous studies, recorded at a limited number of tempe ratures, and display a smooth variation of the lattice parameters over the complete temperature range. No evidence of the suggested low-temp erature phase transitions, or marked premelting effects have been foun d. Detailed measurements of the lattice parameters close to the meltin g point display an anomalous behavior of the b lattice parameter and t he orientation of the molecules which is believed to be evidence of a disordering transition at temperatures above the melting point.