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Petroleum Geochemical Survey
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
The ionic crystal is composed of positive and negative ions. The electro-static attractive forces between two oppositely charged ions (cation and anion) create a strong ionic bond. Sodium chloride is an example of an ionic crystal. The Na+ and Cl– ions surround each other in their fixed crystal lattice site (corner). The ionic crystals are hard and rigid solids with high melting points.
Structural Description of Materials
Published in Snehanshu Pal, Bankim Chandra Ray, Molecular Dynamics Simulation of Nanostructured Materials, 2020
Snehanshu Pal, Bankim Chandra Ray
An ionic crystal has a fixed proportion of anion and cation. This fixed proportion is called stoichiometry of that compound. On the off chance that imperfection in the crystal is with the end goal that the proportion between the cation and anion continues as before as spoken to by its recipe, the deformity is called a stoichiometric imperfection. Stoichiometric deformities are additionally isolated into two types: Schottky defectFrenkel defect
Inorganic Chemistry
Published in Steven L. Hoenig, Basic Chemical Concepts and Tables, 2019
An important property of an ionic crystal is the energy required to break the crystal apart into individual ions, this is the crystal lattice energy. It can be measured by a thermodynamic cycle, called the Born-Habercycle.
An intrinsic criterion of defining ionic or covalent character of AB-type crystals based on the turning boundary radii calculated by an ab initio method
Published in Molecular Physics, 2018
Dong-Xia Zhao, Chun-Yu Yan, Zun-Wei Zhu, Le Zhang, Yi-Ming Jiang, Rui Gong, Zhong-Zhi Yang
As is well known, typically ionic type of crystals, such as NaCl and LiF crystals, have apparently different properties from typically covalent type of crystals, like CuF and diamond crystals. An ionic crystal remarkably differs from a covalent crystal in various physical and chemical behaviours. For instance, an ionic crystal is largely soluble in water, a polar solvent, whereas a covalent crystal is rarely soluble in water. Imaginarily, a typically ionic crystal can be visualised as an assemblage of cations and anions that locate in the crystal in a certain order. For example, a LiF crystal consists of equal number of Li+ and F− ions. However, from both experimental measurement and theoretical consideration, there is no definite answer about how large are the cation Li+ and anion F− and whether they contact each other or not. Pauling pointed out that since electron distribution function of an ion extends indefinitely it is evident that no single characteristic size can be assigned to it. Instead, the apparent ionic radii will depend upon the physical property under discussion. Usually, one is interested in such a kind of ionic radii that the sum of two radii of the cation and anion or anion and anion (with certain corrections if necessary) is equal to the equilibrium contact distance between the corresponding ions in a crystal [1]. Here it should be noticed and emphasised that Pauling et al. had pointed out that the interionic distances for alkali halogenide crystals with the sodium chloride structure do not satisfy the criterion of additivity of the standard ionic radii and attributed this kind of disagreement to the repulsions between ions. Obviously, the contact view of point, a compact packing of ions in the crystal, comes from the idea that this packing resembles a usual packing of macroscopic objects.