The paper clearly showed that the diamond anvil cell could be successfully used to synthesize new materials with novel properties at extreme conditions of high pressures and temperatures. The synthesis of materials at elevated temperatures and pressures is not new, but the conditions at which the synthesis described in our paper has happened are truly remarkable: pressures exceeding half a million atmospheres and temperatures above 2000 K. And what is even more remarkable is that the product could be recovered to ambient conditions.

“There is considerable interest in the synthesis of nitrides because of their technological and fundamental importance and in our paper we have announced the synthesis of a new compound - platinum nitride - which has not been known before.”

There is considerable interest in the synthesis of nitrides because of their technological and fundamental importance and in our paper we have announced the synthesis of a new compound—platinum nitride—which has not been known before. Although numerous metals react with nitrogen there were no known binary nitrides of the noble metals, and our paper has opened up a completely new direction in extreme conditions synthesis.

The paper describes the discovery of platinum nitride, a new compound and the first binary nitride of the noble metals group. It also characterizes this novel material for the first time, in terms of its optical properties, structure, and bulk modulus.

Platinum, being a noble metal, does not react chemically with other compounds or elements under normal conditions. Because it has one of the strongest covalent bonds, nitrogen is also very stable under normal conditions but it does react with some elements, forming interesting compounds with a variety of intriguing properties.

By applying extreme pressures and temperatures to platinum and nitrogen at the same time, we were able to initiate a chemical reaction between them which would not have taken place otherwise. The product of the reaction—platinum nitride—was successfully quenched (recovered) to ambient conditions and is stable. This means that a material that can be created only under very extreme conditions can be examined and characterized—and possibly used—under ambient conditions. We found that its bulk modulus (a measure of how difficult it is to compress) is 30% higher than that of pure platinum, which was not expected and is highly interesting from a materials point of view.

My research is mostly about the behavior of the simple molecular systems (e.g., N₂, H₂, S) under extreme conditions. I have been studying the phase diagram of nitrogen for a number of years using internally heated diamond cells to reach temperatures of the order of 1000 K under pressure. This temperature is roughly the limit that internally heated cells can reach, but we were interested in even higher temperatures and the way to generate them is to use infrared (IR) laser radiation focused on the sample.

By this method one can reach 5000-6000 K, but the problem is that nitrogen is transparent and will not absorb the IR radiation. The way around that is to add what is called a coupler—a thin layer of metal—which will absorb the IR radiation, and thus will heat up and transfer the energy to the surrounding nitrogen.

I chose platinum exactly for the reason described above: it is a noble metal and so I expected that it would not chemically react. After the very first run, I was trying to see whether the nitrogen underwent any of the changes I was looking for, but soon realized that the platinum and nitrogen had reacted, and that the resulting compound was giving an extremely intense Raman signal.

Later on, we conducted x-ray diffraction and ion probe analyses to determine the stoichiometry and the structure of the novel compound. Due to the huge mass difference between nitrogen and platinum, we encountered problems with placing the relatively very light nitrogen atoms in the lattice and actually seeing how many atoms of nitrogen there were in the platinum nitride lattice.

In the original paper we made a mistake and announced that the new compound was PtN. But numerous theoretical papers which appeared shortly afterwards seemed to indicate that this stoichiometry was not possible. In the beginning of 2006, we published another paper simultaneously with other experimental and theoretical groups where the question of the stoichiometry and the nitrogen atomic positions were settled and now the community agrees that the compound is platinum di-nitride, PtN₂, rather than PtN.

For fundamental science, the discovery was very exciting and it did generate a lot of interest in theory work. Experimentalists were slower to react, but, in 2006, several papers—including from our group—appeared, claiming the synthesis of iridium and osmium nitrides. Platinum nitride had a bulk modulus of 375 GPa, and iridium nitride was shown to have a bulk modulus of 428 GPa, the highest bulk modulus of any synthesized material and the second highest bulk modulus after diamond, which is the hardest known material.

I would expect to see more developments in this direction because there is a huge industrial and commercial interest in superhard materials. Also, the same techniques could be used to synthesize novel materials with useful electronic properties such as superconductors.

We are quite far away from producing anything with the diamond anvil cell useful for the industry—the volumes of the synthesized materials are far too small. But one cannot totally write off the possibility of synthesizing a useful material with the diamond anvil cell and later coming up with a clever way of synthesizing the same material by different ways on the industrial scale.

Not at the moment for the same reasons described above—the volumes of the produced material are too small. But if someone synthesizes a very useful material, which would be industrially viable to produce, one can see possible application. For example, it was suggested in the press that iridium and platinum nitrides could eventually replace titanium nitrides which are currently used by the semiconductor industry for surface coatings because of their strength and durability.