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Haflinger, P.S., Gerber, S., Pramod, R., Schnells, V.I., dalla Plazza, B., Chati, R., Pomjakushin, V., Conder, K., Pomjakushina, E., Le Dreau, L., Christensen, N.B., Syljuasen, O.F., Normand, B. and Ronnow, H.M. (2014) Quantum and Thermal Motion, Oxygen Isotope Effect, and Superexchange Distribution in La2CuO4. Physical Review B, 89, Article ID: 085113.

has been cited by the following article:

• TITLE: Crystal Growth of Cu6(Ge,Si)6O18·6H2O and Assignment of UV-VIS Spectra in Comparison to Dehydrated Dioptase and Selected Cu(II) Oxo-Compounds Including Cuprates

  AUTHORS: Hans Hermann Otto

  KEYWORDS: Dioptase, Ge-Dioptase, Copper(II) Compounds, Cuprates, Crystal Growth, UV-VIS Spectroscopy, EPR, Color, d-d Excitations, Bond Strength, Super-Exchange Interaction

  JOURNAL NAME: World Journal of Condensed Matter Physics, Vol.7 No.3, August 21, 2017

  ABSTRACT: Low-dimensional quantum spin systems with the Cu2+ central ion are still in the focus of experimental and theoretical research. Here is reported on growth of mm-sized single-crystals of the low-dimensional S = 1/2 spin compound Cu6(Ge,Si)6O18·6H2O by a diffusion technique in aqueous solution. A route to form Si-rich crystals down to possible dioptase, the pure silicate, is discussed. Motivated by previously reported incorrect assignments of UV-VIS spectra, the assignment of dd excitations from such spectra of the hexahydrate and the fully dehydrated compound is proposed in comparison to dioptase and selected Cu(II) oxo-compounds using bond strength considerations. Non-doped cuprates as layer compounds show higher excitation energies than the title compound. However, when the antiferromagnetic interaction energy as Jz·ln(2) is taken into account for cuprates, a single linear relationship between the Dqe excitation energy and equatorial Cu(II)-O bond strength is confirmed for all compounds. A linear representation is also confirmed between 2A1g energies and a function of axial and equatorial Cu-O bond distances if auxiliary axial bonds are used for four-coordinated compounds. The quotient Dt/Ds of experimental orbital energies deviating from the general trend to smaller values indicates the existence of H2O respectively Cl− axial ligands in comparison to oxo-ligands, whereas larger Dt/Dqe values indicate missing axial bonds. The quotient of the excitation energy 2A1g by 2·2Eg-2B2g allows checking for correctness of the assignment and to distinguish between axial oxo-ligands and others like H2O or Cl−.