What Is the Bulk Modulus?
Bulk modulus is a kind of elastic modulus, which is used to reflect the macroscopic characteristics of the material, that is, a physical quantity of the relationship between the body's strain and the average stress (the average of the three principal stresses at a point).
- bulk modulus
- Material in
- Bulk modulus is a relatively stable material
- Bulk modulus
- Model building
- The bulk modulus of a crystal is related to the stretching ability of a chemical bond. As a result, much work has focused on the relationship between chemical bonds and bulk modulus. The model for calculating the bulk modulus of a semiconductor indicates that the bulk modulus of the crystal is related to the covalent bond energy of the chemical bond per unit volume. Zhang Siyuan et al. Used the chemical bond method to calculate the bulk modulus of the crystal. The model reflects the bulk modulus and the lattice energy per unit volume. Related] These works not only prove that chemical bonds can be used to reflect the bulk modulus of crystals, but also give us a good enlightenment that the bulk modulus of crystals is related to the energy per unit volume.
- The bulk modulus of a crystal is the macroscopic nature of the material, and it reflects the material's resistance to uniform external compression under the elastic system. At the micro level, the bulk modulus of a crystal is determined by the strength and compressibility of the chemical bond, that is, the bulk modulus of the crystal is determined by the resistance of the chemical bond to compression. Since the change in valence electrons is mainly involved in the compression process, it is possible to understand the bulk modulus of the crystal as long as it focuses on the behavior of the valence electrons in the crystal. The electronegativity of an atom describes the interaction between an atom and a valence electron. From another point of view, the greater the electronegativity of the atom, the tighter the atom grabs the electrons, and the more difficult it is for the valence electron cloud to move under external force, so to a certain extent the electronegativity of the atom can indicate that the atom Compression resistance. Further we assume that the resistance of a chemical bond formed by two bonding atoms to external compression can be expressed by the average electronegativity of the two atoms. Since the environment of the atom in the crystal is different from the environment of the molecule, each atom forms a chemical bond with surrounding atoms [CN is the coordination number of the atom, so it is equivalent to only 1 / CN of each chemical bond participating in the bond.
- For polar covalent crystals, the way of bonding is different from pure covalent crystals. Due to the different electronegativity of the two bonding atoms, the valence electron distribution on the chemical bond is uneven, which reduces the resistance of the chemical bond to external compression, that is, the polarity of the chemical bond has a weakening effect on the bulk modulus of the polar crystal. . The greater the electronegativity of an atom, the stronger its ability to attract valence electrons. The end result is an uneven distribution of valence electron clouds and the generation of anions and cations, that is, atoms with different electronegativity lead to the generation of polar bonds. In turn, the generated ionic charge has an attractive effect on valence electrons, alleviating the weakening of the resistance of chemical bonds due to polarity to external compression, so we define effective ionicity to reflect chemical bonds caused by the uneven distribution of valence electrons. Actual weakening of resistance to external compression. [1-2]