Correlated electronic states of nitrogen-based transition-metal pseudo-oxides

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The numerical analysis of the density-functional electronic structures of the 3d transition-metal carbodiimides MNCN (with M = Mn–Cu) as confronted with experiments touching upon their optical and magnetic properties clearly indicates that their true electronic structures cannot be properly dealt with using standard (DFT) solid-state approaches. In particular, local many-electron states and also resonating-valence bond (RVB) states are very likely to be involved. We thus propose to perform a detailed theoretical study of the above family of materials, on the basis of the effective Hamiltonian crystal-field (EHCF) and RVB approaches. In particular, the optical spectra of some of the transparent MNCN and M(NCNH)2 materials (M = Fe–Ni) as well as the Mößbauer spectra of the iron compounds will be calculated in order to establish their many-electron nature. Also, the phase CuNCN will be studied both numerically and analytically such as to quantitatively model and understand the nature ofits (presumably) RVB ground state as indicated by neutron diffraction, SQUID, EPR, NMR and other spectroscopic techniques.