PREDICTING X-RAY-DIFFRACTION INTENSITY DISTRIBUTIONS FOR ONE-DIMENSIONAL INCLUSION-COMPOUNDS VIA LOCAL-DENSITY FUNCTIONAL CALCULATIONS

We investigate whether certain features of the X-ray diffraction (XRD) pattern arising from the guest molecules in one-dimensional inclusion compounds can be predicted and rationalized on the basis of the electron-density distribution computed for the periodic guest structure in the inclusion compound. Specifically, we note that in the XRD patterns of diacyl peroxide/urea inclusion compounds, scattering in reciprocal lattice planes (hkl)g with odd I is significantly more intense than that in the adjacent reciprocal lattice planes with even I, whereas for alkane/urea inclusion compounds there is a monotonic decrease in intensity as I is increased. Local density functional methods have been used to compute the electron-density distributions for the guest structures in the dioctanoyl peroxide/urea and decane/urea inclusion compounds; and the methodology required to use this information to calculate the XRD intensities 1(hkl)g , as a function of I index, is described. It is demonstrated that XRD intensity distributions derived from the computed guest electron densities do indeed predict correctly the contrasting relationships between 1(hkl)g and I, observed experimentally, for the diacyl peroxide/urea and alkane/urea inclusion compounds.