Electronegativity And Bulk Moduli Of Inorganic Materials

The macroscopic properties are determined by the actions between atoms because materials are formed through the self-assembly of atoms in certain conditions. Electronegativity (EN) is an important parameter to scale atomic property, which was defined as "the power of an atom in a molecule to attract electrons to itself". EN is a useful tool to establish the relations between the microscopic structure and the macroscopic properties due to the combination of the subjects of material, physics, and chemistry. On the other hand, much attention is focused on superhard materials due to their importance in industry. It is of significance to investigate the bulk modulus of crystals due to the fact that superhard materials often possess large bulk modulus. The purpose of this thesis is to investigate the bulk modulus of inorganic crystals from the viewpoint of EN.The bulk modulus of crystals reflects the resisting ability of crystals to uniform compression, which is essentially determined by the resisting ability of chemical bonds to compression. Two key parameters, bond modulus and effective ionicity, are used to describe the resisting ability of chemical bonds to compression on the basis of EN. Further, we proposed a model to calculate the bulk moduli of simple crystals. We found that the bulk modulus of crystals is mainly determined by bond modulus for compounds of high cationic valences while that is determined by both of bond modulus and effective ionicity for compounds of low cationic valences. The calculated bulk moduli of ANB8-N crystals, oxides and nitrides agree well with the experimental values.The model of calculating the bulk moduli of simple crystals is extended to estimate the bulk moduli of complex crystals and alloys, which are composed of different types of chemical bonds. We proposed the calculation procedures of the bulk moduli of complex compounds on the basis of bond strength difference between different bonds. For compounds of small bond strength difference, the bulk modulus is determined by the average resisting ability of chemical bonds to compression while for that of large bond strength difference, the bulk modulus is determined by the resisting ability of weaker bonds to compression. The consistency between the calculated bulk moduli and the experimental data of chalcopyrites, spinels, and ABO4 compounds confirms this model. Based on this model, we also predicted some low compressibility crystals.