Hardness Of Rare Earth Functional Materials

The mechanical properties of functional materials have been one of the hottest topics in the field of novel materials research. The basis of the study on the mechanical properties of functional materials is to profoundly understand their micro structures and to find the relationship between their properties and microstructure. Electronegativity characterizes the ability of an atom in molecule to attract electrons to itself, and became an important parameter to study the properties of materials after80years’development. Hardness of materials is one of the mechanical properties of materials, which is used to characterize the ability of a solid to resist elastic and permanent plastic deformations and closely related to some practical applications of materials. Hardness prediction of functional materials in terms of electronegativity can provide some implications to design novel functional materials.In this thesis, we have calculated17rare earth elements electronegativity values with different coordination numbers in crystals. We found that the lanthanides covalent electronegativity values increase with increasing the lanthanides atomic numbers, and show an obvious "gadolinium break" phenomena. Based on available experimental hardness values of rare earth functional materials, we established a formula to express the hardness rare earth functional materials in terms of the newly proposed electronegativity, which was further expanded to predict the hardness of other rare earth functional materials. We found an agreement between our calculated and experimental hardness values, which indicates the prediction power of our newly proposed hardness expression of rare earth functional materials. Finally, we observed an increase of calculated hardness with increasing atomic numbers of lanthanide elements and an obvious "gadolinium break" phenomena for rare earth functional materials with same structures.