Band Gap And Bulk Modulus Of Inorganic Materials

Inorganic materials have been received a lot of attention for its important applications in industrial production and our daily life. Band gaps (Eg) and bulk modulus (B) are two important parameters which reflect the optoelectronic and mechanical properties of materials, respectively. Over the years, many theoretical efforts have been devoted to revealing the origin of band gap and bulk modulus, as well as band gap and bulk modulus calculation. In addition, lots of experimental works also have been carried out to measure band gap and bulk modulus of materials. However, there is few work involved about relationship between band gap and bulk modulus of materials. Actually, successful fabrication of optoelectronic devices also requires better understanding of the mechanical properties of materials since the contact loading during processing or packaging can significantly degrade the optoelectronic properties of the devices. The macroscopic properties of materials are mainly determined by the constituent atoms and chemical bonds, which can be effectively reflected by electronegativity (EN). Researchers have carried out many investigations about material properties and material design successfully on the basis of EN viewpoint.By using the EN-related models for bulk modulus and band gap, this work quantitatively calculated the bulk moduli and band gaps of ZnO-based alloys in the whole composition rang, including BexZn1-xO, MgxZn1-xO, CaxZn1-xO and CdxZn1-xO. We found that the change trends of bulk modulus and band gap with an increase of M concentration x are same for BexZn1-xO and CdxZn1-xO, while the change trends are reverse for MgxZn1-xO and CaxZn1-xO. Based on the analysis of the nature of bulk modulus and band gap, this work proposed that bulk modulus is related to the valence electron density of atoms whereas the band gap is strongly influenced by the detailed chemical bonding behaviors of constituent atoms.From the viewpoint of chemical bond, this work presented that the total valence electrons could be separated into the delocalized and localized parts. The delocalized part denotes those electrons which delocalize the valence basin and has relatively high energy. Therefore, delocalized electrons with high energy state can be excited easily, while it is difficult for localized electrons to be excited. The band gap is an excited state property, which is highly dependent on the delocalized electrons. Quantitative linear relations between band gap and bulk modulus for each type of binary ANB8-N semiconductors were established. The ratio of band gap to average bond volume is defined as the excited energy density of chemical bonds (μ) which reflects the resisting ability of delocalized electrons of chemical bonds to compression. The slope of linear relation between μ and B is a function of the valence state and coordination number of cations. Moreover, this work extend the quantitative correlation to calculate the band gap of ternary chalcopyrite semiconductors by considering the cation d state effects. The calculated results agree with the experimental values, indicating that the quantitative equation clarifies the intrinsic correlation between band gap and bulk modulus.