Investigation of M�ssbauer parameters for a set of iodine compounds using gradient-corrected density functional theory

In the present work we show the first application of density functional theory (DFT) with gradient-corrected exchange-correction functionals within the linear combination of Gaussian-type orbitals (LCGTO) formalism to the calculation of isomer shifts and quadrupole couplings for a large and varied set of iodine compounds: I2, ICl, IBr, ICN, HI, KI, CH3I, CH2I2, CHI3, CI4, SiI4, GeI4, and SnI4. The results are compared with experimental data from Mössbauer spectroscopy. The overall agreement with experiment is most satisfactory, with the exception of the highly dipolar systems ICl, IBr, and ICN. For these systems it is believed that the free molecule assumption of the calculations is not an entirely valid model of the crystalline environment of the experiments.