The geometries in the staggered and eclipsed conformations of the metallocenes, M(C5H5)2 with M = Mn, Fe, Co, Ni, and Ru, have been calculated at the local and nonlocal density functional theory (LDFT and NLDFT) levels. The M−C distance is predicted to be too short at the LDFT level and too long at the NLDFT level. The doublet low-spin states for M = Mn and Co show distortions away from the idealized fivefold symmetries. The low-spin state for M = Mn is predicted to be lower in energy than the high-spin state in contrast to the observed experimental results. The size of the splitting is strongly dependent on the computational level. The values of α and γ were calculated for the various metallocenes. The highest value of γ was found for M = Co.

An optical storage technique based on the characteristic absorption bands of J aggregates of organic dyes is reported. The information is written by disordering the regular structures of cyanine dye J aggregates with a laser beam. This technique gives high recording sensitivity, and the disordered dye molecules can be made to reform the J aggregate, which indicates that the recording process is reversible. The J aggregates of cyanine dyes were formed by incorporating them in Langmuir–Blodgett (LB) films. The advantages of the narrow absorption bands of J aggregates and of the controlled multilayer forming capability of LB films were combined to demonstrate multiple wavelength optical recording using two recording layers.

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