Lattice dynamical calculation of first-order thermal diffuse scattering in phenothiazine

A computer program has been developed to calculate first-order thermal diffuse scattering (TDS) intensity from eigenvectors and eigenvalues of the dynamical matrix obtained within the harmonic approximation with an atom-atom potential function and the external Born-von Kármán formalism. It is applied to monoclinic phenothiazine and correction factors of Bragg intensities due to TDS contribution are calculated and compared with the long-wave approximation. A Fourier difference synthesis is performed in order to reveal the influence of TDS contributions in electron density maps. A least-squares process is carried out to obtain the changes in structural parameters due to TDS contribution.