The crystal strucure of Calcium oxide

Description

Calcium oxide is a white crystalline substance (an inorganic compound) having the chemical formula CaO. Its common name is quicklime. Calcium oxide comprises one calcium (Ca) atom and one oxygen (O) atom, with a chemical formula of CaO. Calcium oxide has a melting point of approximately 2,572 degrees Celsius (4,662 degrees Fahrenheit). It has a high density, so it is a heavy substance.

Preparation

Calcium oxide (CaO), known as quicklime, is widely used. It is a white, caustic, alkaline solid at room temperature. As a commercial product, lime often contains MgO, silicon oxide (sand), and smaller amounts of aluminum and iron [1]. This is due to the fact that “limestone” contains these impurities. It is primarily CaCO3, which, when fired at high temperatures, forms CaO:

CaCO3 + heat ⇒ CaO + CO2

This is accomplished by heating the material to about 825 °C, a process called “calcination” or lime burning, to liberate a molecule of CO2, leaving “quicklime.” This process is reversible since once the quicklime product has cooled, it immediately begins to absorb carbon dioxide from the air until, after enough time, it is completely converted back to calcium carbonate.

Structure

CaO is Halite, Rock Salt structured and crystallizes in the cubic Fm̅3m space group. Ca²⁺ is bonded to six equivalent O²⁻ atoms to form a mixture of corner and edge-sharing CaO₆ octahedra. The corner-sharing octahedra are not tilted. All Ca-O bond lengths are 2.40 Å. O²⁻ is bonded to six equivalent Ca²⁺ atoms to form a corner and edge-sharing OCa₆ octahedra mixture. The corner-sharing octahedra are not tilted.

Reference

[1] Han Zhang. “Defect Study of MgO-CaO Material Doped with CeO2.” Advances in Materials Science and Engineering 2013 1 (2013): 1–5.