Rietveld refinement using synchrotron powder diffraction data for curcumin, C21H20O6, and comparison with density functional theory

Synchrotron powder diffraction data from beamline 08B1-1 at the Canadian Light Source have been used to examine the structure of curcumin, a prime component of the Asian spice turmeric. Rigid body refinement, with the application of restraints on distances and angles, was performed with the Rietveld software package GSAS yielding monoclinic lattice parameters of a = 12.6967(1) Å, b = 7.198 52(3) Å, c = 19.9533(2) Å, and β = 95.1241(6)° (C 21 H 20 O 6 , Z = 4, and space group P 2/ n ). The refinement was compared with a recent single-crystal structure and ab initio results obtained with density functional theory calculations.