A Chemistry Revolution

Model of NaCl3  Credit:  Artem Organov and Weiwei Zhang
Model of NaCl3 Credit: Artem Organov and Weiwei Zhang

We all know NaCl is table salt. Ever heard of NaCl3?  Or Na3Cl?

Table salt, also known as sodium chloride or NaCl, is one of the best-known and most studied chemical compounds.  Its chemical composition is simple – one sodium atom (Na) and one chlorine atom (Cl). Classical chemistry says atoms try to fulfill the octet rule — elements gain or lose electrons to attain an electron configuration of the nearest noble gas, with complete outer electron shells that make them very stable.  Sodium has one extra electron and chlorine is missing one, so sodium donates one electron to chlorine, leaving both atoms with an outer shell containing eight electrons and forming a strong ionic bond.

Artem R. Oganov, professor of theoretical crystallography in the Department of Geosciences at Stony Brook University, is causing quite a stir challenging the foundation of chemistry. Oganov’s lab has produced novel compounds by applying high pressure.  They heated samples of table salt under pressure with lasers and found new compounds of Na and Cl which came as a surprise. The new compounds are stable and, once made, remain indefinitely.

Model of NaCl3  Credit:  Artem R. Oganov & Weiwei Zhang
Model of NaCl3 Credit: Artem R. Oganov & Weiwei Zhang

Among the compounds Oganov and his team created are two-dimensional metals, where electricity is conducted along the layers of the structure. “One of these materials – Na3Cl – has a fascinating structure,” Oganov says. “It is comprised of layers of NaCl and layers of pure sodium. The NaCl layers act as insulators; the pure sodium layers conduct electricity”.

The experiments with table salt might only be the beginning of the discovery of completely new compounds.  Understanding and predicting high-pressure compounds can lead to new theories with applications for atrophysics and planetary sciences, where high pressure abounds.

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