Quantum mechanical calculations of Fe-bearing silicates

The basic aim of this proposal is to understand the relation between the magnetic structure on the one hand and the electronic and geometrical structure on the other hand of some important rock-forming Fe-silicates and their solid solutions with their isotypic Mg- and Al-silicates. This relation is not yet thoroughly understood. At low temperatures, Fe-bearing silicates exhibit a variety of interesting magnetic properties reflecting occasionally peculiarities of their crystal structures and therefore are well suited objects of such a study. In order to achieve this goal, systematic ab initio electronic structure calculations on the basis of experimentally determined crystal structures will be performed from which spin density distributions, magnetic moments, and magnetic interaction constants can be derived. The most appropriate theoretical basis for electronic structure calculations on transition metal compounds, such as Fe-silicates, is provided by the density functional theory applied here in form of the local spin density approximation. Experimental spectroscopic and crystallographic data (Moessbauer, neutron diffraction) are then used on the one hand to judge the reliability of the calculations. On the other hand the experimental data can be explained in more detail by the theoretical results. Because the magnetic effects contribute to a certain extent to the thermodynamic properties of Fe-bearing silicates, these aspects will also be discussed. Results and conclusions will be of general interest for the structure-property relation of magnetic materials. Currently, there is an increasing commercial and industrial interest in different kinds of magnetic materials.

The basic aim of this proposal is to understand the relation between the magnetic structure on the one hand and the electronic and geometrical structure on the other hand of some important rock-forming Fe-silicates and their solid solutions with their isotypic Mg- and Al-silicates. This relation is not yet thoroughly understood. At low temperatures, Fe-bearing silicates exhibit a variety of interesting magnetic properties reflecting occasionally peculiarities of their crystal structures and therefore are well suited objects of such a study. In order to achieve this goal, systematic ab initio electronic structure calculations on the basis of experimentally determined crystal structures will be performed from which spin density distributions, magnetic moments, and magnetic interaction constants can be derived. The most appropriate theoretical basis for electronic structure calculations on transition metal compounds, such as Fe-silicates, is provided by the density functional theory applied here in form of the local spin density approximation. Experimental spectroscopic and crystallographic data (Moessbauer, neutron diffraction) are then used on the one hand to judge the reliability of the calculations. On the other hand the experimental data can be explained in more detail by the theoretical results. Because the magnetic effects contribute to a certain extent to the thermodynamic properties of Fe-bearing silicates, these aspects will also be discussed. Results and conclusions will be of general interest for the structure-property relation of magnetic materials. Currently, there is an increasing commercial and industrial interest in different kinds of magnetic materials.