A novel approach to the calculation of powder lineshapes is presented,
Lineshapes from asymmetric second-rank tensor interactions are produc
ed by summing lineshapes from symmetric tensors. This approach signifi
cantly reduces the calculation time, greatly facilitating iterative no
nlinear least-squares fitting of experimental spectra. Results are rep
orted for anisotropic C-13 NMR lineshapes of glycine, benzoic acid, an
d octanoic acid in a urea inclusion compound. Lineshapes from nonunifo
rm distributions of crystallite orientations can also be calculated by
using distributions of the Euler angles that define the orientation o
f the principal-axis system of the chemical-shielding tensor with resp
ect to the magnetic field. (C) 1996 Academic Press, Inc.