Investigation of the electronic structure and chemical bonding of lead hexacyanoferrate(III)

The electronic structure of lead hexacyanoferrate(III) is calculated by the ab initio tight-binding linear muffin-tin orbital (TB-LMTO) method in the LSDA + U approximation. The influence of vacancies in the lead sublattice on the electronic spectrum, chemical bonding, and magnetic properties of the Pb_1.5Fe(CN)₆ phase is investigated. Analysis of the electronic spectrum shows that this compound is characterized by semiconductor conductivity. It is demonstrated that the semiconductor gap is associated with the charge ordering of iron(III) ions.     

Elastic and kinetic properties of single-crystal La<Subscript>0.75</Subscript>Ba<Subscript>0.25</Subscript>MnO<Subscript>3</Subscript>

An experimental study of the temperature behavior of longitudinal sound velocity, internal friction, electrical resistivity, and thermopower of single-crystal La_0.75Ba_0.25MnO₃ is reported. A structural transition accompanied by a large jump (18%) in the sound velocity was found to occur at T _S ≈170 K. Within the interval 156–350 K, the temperature dependences of the sound velocity and internal friction reveal a temperature hysteresis. An internal-friction peak due to relaxation processes was detected. The metallic and semiconducting regions are separated by a transition domain about 80 K wide lying below the Curie temperature T _C =300 K.     

Specific features of the formation of oxygen defects in the SrFeO2.5 ferrate with a brownmillerite structure

The electronic structure and chemical bonding in the Sr₂Fe₂O₅ strontium ferrate are investigated in the framework of the ab initio linear-muffin-tin-orbital tight-binding representation and extended Hükcel calculations. Models of defect formation (oxygen vacancies and anti-Frenkel defects) in the brownmillerite structure are considered. A model of ion transfer in strontium ferrate is proposed reasoning from the results of the calculations.     

ChemInform Abstract: Anhydrous Tin and Lead Hexacyanoferrates(II). Part 2. Electronic Structure and Chemical Bonding

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