Chemistry textbooks will tell you that you need at least two different elements to produce an ionic material. So, what to make of a paper in the journal Nature by Artem Oganov of the Swiss research center, ETH Zurich, and colleagus have simulated a superhard form of boron that contains ionic bonds.
The team was developing a computational method to help them predict the structure of various types of material and applied the technique to a newly synthesized form of pure boron that possesses some
unusual physical properties.
They were surprised to discover that this novel boron was more unusual than they could have imagined, revealing a degree of ionic bonding between boron atoms, that theoretically should not exist, but apparently do.
The new structure can be viewed as a NaCl-type structure, with anionic and cationic positions occupied by two different clusters of boron atoms (B12 and B2). The difference of the electronic properties of these clusters brings about charge transfer, making this material a partially ionic boron boride. the press release on this work says that boron is the chemical element most susceptible to changes in structure due to the presence of impurities. Maybe that’s the explanation…but of course it cannot be so, this is a computer simulation, there are no impurities.
The discovery could mark an important step towards a better understanding of boron. But, perhaps more intriguingly is that it beggars questions about what we mean by a chemical bond…