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Microscopic insight into properties and electronic instabilities of impurities in cubic and lower symmetry insulators: the influence of pressure.
The phenomena associated with the Jahn-Teller effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu(2+) are discussed.
Origin of the exotic blue color of copper-containing historical pigments.
The origin of the unusual bright blue color displayed by historical Egyptian Blue and Han Blue pigments that is surprisingly not found in other compounds like BaCuSi2O6 or CaCuO2 containing the same CuO4(6-) chromophore is investigated by means of ab initio calculations.
Changing the Usual Interpretation of the Structure and Ground State of Cu2+-Layered Perovskites
Intense research studies on hybrid organic–inorganic-layered copper perovskites are currently being carried out. Many interesting properties of these materials rest on the strong correlation between
Colour due to Cr3+ ions in oxides: a study of the model system MgO:Cr3+.
The calculated electrostatic potential, VR(r), related to ER(r,), is found to be attractive when the electronic density is lying along <110> directions and |r| > 1 Å driven by the first shell of twelve Mg(2+) ions.
Origin of the Anomalous Color of Egyptian and Han Blue Historical Pigments: Going beyond the Complex Approximation in Ligand Field Theory.
The complex approximation is widely used in the framework of the Ligand Field Theory for explaining the optical properties of crystalline coordination compounds. Here, we show that there are
Electrostatic Control of Orbital Ordering in Noncubic Crystals
In noncubic insulating crystals where active orbitals are not degenerate the usual models to describe orbital ordering, Kugel–Khomskii and Jahn–Teller, are, in principle, not valid. For these
Compounds Containing Tetragonal Cu2+ Complexes: Is the dx2–y2–d3z2–r2 Gap a Direct Reflection of the Distortion?
It is widely assumed that the gap, Δ, between dx2–y2 and d3z2–r2 orbitals in fluorides and oxides containing tetragonal Cu2+ or Ag2+ complexes directly reflects the tetragonal distortion in the MX6
Cu2+ in layered compounds: origin of the compressed geometry in the model system K2ZnF4:Cu2+.
Results of ab initio periodic supercell and cluster calculations on K2ZnF4:Cu(2+), showing unequivocally that the actual origin of the unusual compressed geometry of the CuF6(4-) complex along the crystal c axis in that tetragonal lattice is due to the presence of an electric fielddue to the crystal surrounding the impurity.