Life can only exist in a narrow range of pressures and temperatures, and chemistry and physics is mainly focused around the study of these “normal”, life-permitting conditions. But recent advances in high-pressure chemistry and physics have made it possible to break open these limitations, reaching ultra-high pressures and temperatures in laboratories (up to 4 million times the atmospheric pressure and as high as 3700 degrees), giving access to materials with unusual structural, electronic and magnetic properties. Even more extreme conditions occur in detonations of high-energy materials, in the interior of planets, or in comet collisions.

Normal chemistry changes dramatically at high pressures: chemical bonds break and new ones form, hydrogen becomes metallic, nitrogen forms strands, and lithium liquifies. Distances between atoms decrease, and both electronic and structural modifications can lead to new and unexpected electronic properties.

High pressure may also have played an important role in the origins of life and in the synthesis of the first biologically relevant organic molecules such as amino acids. Discovery of abundant life in high-pressure environments such as the deep-ocean, hydrothermal vents or crustal rocks shows that life is able to adapt to such extreme and harsh conditions.

Development of new materials

Studies of atoms and molecules at high pressure stretches current chemical intuition and leads to the development of new materials with novel structural, electronic and magnetic properties. Materials’ chemistry under ultra-high pressure is an important emerging research area, opening up exciting new routes for stabilising unusual and interesting compounds. A clear theoretical framework is, however, needed in order to gain a deeper understanding, and predict new chemistry and physics while guiding the difficult experiments.

In a new project, funded by a Marsden grant, Distinguished Professor Peter Schwerdtfeger and Dr Elke Pahl from the Centre for Theoretical Chemistry and Physics at the New Zealand Institute for Advanced Study at Massey University, Albany, with support from postdoctoral fellows Dr Krista Steenbergen and Dr Paul Jerabek and PhD students Odile Smits and Lukas Trombach, are working to create just such a theoretical framework to gain a deeper understanding of high-pressure physics.

To do this, they are developing state-of-the-art computational methods in order to investigate high-pressure materials as accurately as can be achieved in experiments. Simulations are being carried out at Massey University’s high-performance computer cluster, coupled with the use of sophisticated quantum chemistry software packages.

Previously, the team has successfully simulated the liquid-to-gas transition of mercury, explaining for the first time why it has such a low boiling point compared to the lighter elements in the periodic table. Their results showed that due to Einstein’s special relativity, mercury becomes chemically more inert, lowering the transition temperature by 300 degrees.