Study On Electronegativity And Borate Crystal

Borate crystals, as successful nonlinear optical (NLO) materials, have attracted much attention by scientists, since there are varieties of borates and many of them have complex structures. Electronegativity (EN) has been widely used as an essential parameter in the fields of materials, chemistry and physics, and as an important means for the study of the structure-property relationship of crystal materials. It has been proved that EN is closely related to many properties of materials such as optical properties, hardness, superconductive, and magnetic. In this thesis, we have proposed a formula for the calculation of electronic polarizability of borate crystals on the basis of EN. At the same time, EN has been applied in the study o the conditions on which the Fundamental Building Block (FBB) of borate crystals are formed.The electronic polarizability of a material typifies the distortion of the electron clouds and is closely related to the properties of the material, thus it has been an important parameter in the design of optical-electric materials. The electronic polarizability of borate crystals is strongly depedent on the electronegativity of its constituent atoms. And the electronic polarizability of an atom is mainly affected by the following two factors. The one factor is the ability of the effective nuclear charges to attract the valence electrons in outer orbital, and the other factor is the distortion of the outer electrons. Based on the average EN and the principal quantum number of the atoms in borate crystals, an electronic plarizability formula of borate crystals has been proposed, and the refractive indices of some borate crystals has been predicted by using the Lorenz-Lorentz equation.The chracteristics of the formation of FBB of borate crystals has been studied by employing the EN concept. A new method for calculating the group EN values is proposed in accordance with the Sanderson electronegativity equalization principle and then the EN of the FBB of borate crystals was calculated by the progressive geometric method. The group EN values of the isolated or branch structured FBB is found to be larger than that of the ring structured FBB. While combined with cations that have large average electronagetivities, the ring structured FBB of borate crystals are usually not found, only the isolated or branch structured FBB are formed. Two fundamental parameters, k and X, which represent the number ratio of the cations to boron atoms and the electronegativity of the cations, respectively, have been employed to predict the formation condition of the ring structured FBB. It is found that the ring structured FBB are usually be formed under the conditions k≤1 and X＜1.