| Abstract: | Most important supposition for a possible site preference in a olivine solid-solutions are besides the different crystal chemical properties of M cations (size, electronegativity, crystal field stabilization energy) the differences between the both octahedral coordinated sites M1 and M2 of the olivine structure. Using this regularities the site preference in the system Ni Co olivines is predicted. If site preferences are existing, it is possible to deduce deviations of the Vegard's rule in the system Ni2SiO4—Co2SiO4 using geometrically-structurally considerations. The plot of experimentally determined lattice parameters in this solid solutions system shows the existing of the proposed deviations of the Vegard's rule and evidences the site preferences of Ni2+ in the M1- and Co2+ in the M2 octahedra only by determination of lattice parameters. |
