Scientists turn table salt into forbidden compounds that violate textbook rules

In the field of exotic new materials, we've examined one of the strongest ones and another declared to be impossible; scientists now report creating "forbidden" materials out of ordinary table salt that violate classical rules of chemistry. Not only does the development challenge the theoretical foundation of chemistry, but it is also expected to lead to the discovery of new exotic chemical compounds with practical uses and shed light on the deep interiors of planets.

The international team of researchers led by Artem R. Oganov, a Professor of Crystallography at Stony Brook University, predicted that taking table salt and subjecting it to high pressure in the presence of an excess of one of its constituents (either chlorine or sodium) would lead to the formation of totally unexpected compounds. In spite of salt being one of the most thoroughly studied chemical compounds out there, the researchers predicted the formation of compounds forbidden by classical chemistry, such as Na3Cl and NaCl3. Their predictions were proven by subsequent experiments.

"Sodium has one electron in its outermost shell, and chlorine has seven," Weiwei Zhang, the lead author, a Professor of Physics at China Agricultural University and visiting scholar at Oganov's lab, tells Gizmag. "When sodium meets chlorine, sodium would like to give away an electron and chlorine wants to take one according to the Octet rule. Since one Na can supply only one electron to one Cl, the only possible combination of these atoms in a compound is 1:1, rocksalt NaCl. Take NaCl3 as an example, when you try to satisfy three Cl by one Na, there is no way to distribute electrons according to this rule. So NaCl3 is forbidden in the classical frame of chemistry."

In addition to NaCl3, the team has predicted other new "crazy" compounds, such as NaCl7, Na3Cl2, Na2Cl, and Na3Cl, based on a sophisticated algorithm developed by Oganov and his students involving quantum-mechanical calculations. The experiment verified their prediction that these exotic materials would be thermodynamically stable at high pressures. Their research opens up the way to successfully create and stabilize a huge number of compounds previously considered to be forbidden.

Link: http://www.gizmag.com/scientists-create-forbidden-compounds-table-salt/30520/