Calculation of the electronic structure of spin-crossover complexes and of biomolecules with exchange-coupled spins using density functional theory methods

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Electronic structure calculations on metallo corrolates and on spin-crossover complexes shall be performed applying density-functional theory (DFT). The corrolates are the subject of controversy as to how their magneto-structural properties are influenced by ligand substitutions. By combining Mössbauer and NMR spectroscopy and DFT calculations we are aiming to characterize the properties of these complexes. Spin-crossover complexes exhibit a reversible transition from the high-spin (HS) to the low-spin (LS) state; they are promising materials for optical information storage and display devices. The calculations will be performed for molecules in vacuo, for molecules in solution (using a continuum model to simulate the influence of solvents) and for a unit cell or a supercell with periodic boundary conditions. In the latter case the Car-Parrinello molecular dynamics method with pseudopotentials and plane waves will be used. This method allows also to investigate the influence of pressure. We expect to derive information about the differences of energy and entropy between LS and HS state, on the transition temperature and on the form of the transition curve. The calculations will be accompanied by experimental studies using Mössbauer and Raman spectroscopy and nuclear inelastic scattering of synchrotron radiation.