材料期刊网

A theoretical method for studying the inter-relation between electronic and molecular structure has been proposed by diagonalizing the complete energy matrices for a d(5) configuration ion in a trigonal ligand field and considering the second-order and fourth-order EPR parameters D and (a - F) simultaneously. As for ZnSiF6 center dot 6H(2)O:Mn2+ and ZnSiF6 center dot 6D(2)O: Mn2+ complex molecules, the local lattice distortion and local thermal expansion coefficient for the octahedral Mn2+ centers in zinc fluosilicate have been investigated, respectively. The calculations indicate that the local lattice structure around an octahedral Mn2+ center has an expansion distortion, whether the Mn2+ ion is doped in ZnSiF6 center dot 6H(2)O or ZnSiF6 center dot 6D(2)O. Moreover, the total tendency of the local lattice expansion distortion will be more and more obvious with the temperature rising, apart from some slight variations at T = 60 K for the ZnSiF6 center dot 6H(2)O. By simulating the two low-symmetry EPR parameters D and (a - F) simultaneously, the local lattice structure parameters R and theta have been determined to vary from 2.204 angstrom to 2.256 angstrom and from 53.417 degrees to 52.71 degrees, respectively, in the temperature range 19-297 K for ZnSiF6 center dot 6H(2)O:Mn2+ and to vary from 2.215 angstrom to 2.255 angstrom and from 53.346 degrees to 52.714 degrees, respectively, in the temperature range 50-300 K for ZnSiF6 center dot 6D(2)O:Mn2+. Subsequently the dependence of local thermal expansion coefficients on the temperature is studied and the corresponding theoretical values of the local thermal expansion coefficients are reported firstly. Some characteristics of local thermal expansion coefficients of Mn2+ in ZnSiF6 center dot 6H(2)O:Mn2+ and ZnSiF6 center dot 6D(2)O:Mn2+ systems are also analyzed.