We report a semiempirical method for the evaluation of bond covalency in complex crystals. This method is the extension of the dielectric description theory delivered by Phillips, Van Vechten, Levine, and Tanaka (PVLT) which is mainly suitable for binary crystals. Our method offers the advantage of applicability to a broad class of complex materials. The simplicity of the approach allows a broader class of researchers to access the method easily and to calculate not only the bond covalency but also other useful properties such as bulk modulus. For a series study, a useful trend can be illustrated and often the prediction of the properties of the missing one(s) among the series can be possible. Finally, examples are given to show how the method is applied and the procedure is transferable to other complex crystals.

A semiempirical method for the evaluation of the barycenter of energy of 4f N-1 5d configurations is presented. The environmental factors affecting the barycenter are given to be the bond volume polarization, fractional covalence of the chemical bond between the central ion and the nearest anion, and presented charge of the nearest anion in the chemical bonds. The barycenter energies of 4f N-1 5d configurations of Eu 2+ and Ce 3+ are calculated in various crystals, and the results are in good agreement with the experimental values. A relationship is found between the barycenter of energy of the 4f N-1 5d configuration on Eu 2+ and Ce 3+ ions and environmental factors. Our method offers the advantage of applicability to a broad class of luminescence materials and initiates a link between macroscopic properties and microscopic structure.

These results indicate that endogenous AM2 might be involved in energy metabolism in adipocytes through the upregulation of UCP1 expression.