Theoretical chemistry is a growing research field, partly because it has proved to be a useful tool in explaining everything from the chemistry of the stars to how the retina in our eyes can see infrared light. Professor Trygve Helgaker, the Director of the Hylleraas Centre for Quantum Molecular Sciences, explains the usefulness by the fact that theoretical chemistry is a generic tool that can be widely used.
Remember those pixelated photos that you took with your cell phone in 2003? Today, the resolution is enormously improved. Similarly, theoretical chemistry can zoom in on atoms and molecules to see what happens, in space and time, at a much higher resolution today than in 2003. The ability to study chemical reactions in this manner has been incredibly useful, which is one reason the Research Council has awarded Trygve Helgaker two Centres of Excellence in a row: The Centre for Theoretical and Computational Chemistry (CTCC) in 2007 and now the Hylleraas Centre. Both centres are a cooperation between the University of Oslo and University of Troms? – The Arctic University of Norway, with the University of Troms? as host institution of CTCC and Oslo as host institution for the Hylleraas centre.
- The group that could be the most beneficial to life sciences
- There are a lot of things we couldn?t have done if the CTCC hadn?t worked out as well as it did. When it was established, the groups working with theoretical chemistry in Oslo and Troms? were very small. In Oslo, it consisted of professor Knut F?gri and myself, professor Trygve Helgaker explains. The group was so small that we realized we needed to cooperate with Troms? for sufficient impact and credibility. We also cooperated with experimentalists.
Prior to CTCCs establishment, there were only two permanent staff in theoretical chemistry at the University of Oslo: professor Trygve Helgaker and professor Knut F?gri, plus three students and a postdoc. Professor Thomas Bondo Perdersen was later recruited to work in electronic structure theory.
- We recognized the increasing importance of life sciences, says Helgaker, which is why we put such efforts in that direction. In a discussion with the Head of Department at the time, Svein Stølen, I argued that theoretical chemistry was the group that could be most beneficial to life sciences in our department, given the necessary support.
This is how we can see the “invisible”
St?len was sufficiently convinced to support the recruitment of more permanent staff for the group, including professor Michele Cascella, an expert in multiscale modelling with applications in biological systems. Multiscale modelling allows us to study much larger systems than the relatively small ones that can be studied by quantum chemistry. In this way, complex systems with thousands of atoms can be studied, treating only the most important ones quantum mechanically.
- Using advanced multiscale modelling, Cascella has explained the curious fact that we sometimes can see infrared light. This should not be possible since infrared radiation consists of photons that do not have enough energy to affect the sensors in our eyes.
- However, if two infrared photons hit these sensors at the same time, they will together have enough energy to be registered and be perceived as light. For this to be possible, the infrared radiation must be sufficiently intense so that the probability of two photons hitting the same sensor molecule at the same time is high. This is just one example of how theoretical chemistry can be beneficial to life sciences.
Professor Odile Eisenstein had also been an important resource at the CTCC. While employed in a 20 % position, she has helped recruit excellent young researchers such as David Balcells. In total, there are now five permanent scientific staff at the Hylleraas Centre in Oslo.
- To hit a molecule with a laser pulse is an extreme action
With new experimental facilities come new opportunities. Recently, 4th generation light sources have made it possible to study complex processes that could otherwise not have been studied in a controlled environment.
- To hit a molecule with a laser pulse is an extreme action. It is not difficult to do, but it can be very complicated to understand how the molecule responds, says Helgaker.
He has experience with chemistry under extreme conditions—for instance, molecules in a magnetic field a hundred times stronger than those created on Earth. Such conditions exist on some white dwarfs, the final evoluationary state for a medium-sized star such as our sun.
- We have discovered that a new type of chemical bonding occurs in the strong magnetic fields on white dwarf stars. Today, astrophysicts observe atoms in the atmospheres of magnetic white dwarfs and their spectra are used to determine the field strengths of the stars. So far, molecules have been observed only on the non-magnetic white dwarfs. There is every reason to believe they also exist on magnetic white dwarfs but, without prediction of their spectra, we do not know what to look for. An ongoing project in our group is to calculate such spectra.
Norwegian champions in crunching numbers
The Hylleraas Centre uses over 40 million CPU hours a year, making it one of Norway’s biggest consumers of computer power.
- We do number crunching – not much input nor output, but a lot happens in between. Our biggest challenge is efficient use of parallel processing. We may be forced to change our computational models and rewrite our programs to harness the enormous power of tomorrow’s computers, consisting of thousands of processors, says Helgaker.
Even small molecules consist of many electrons and nuclei, making the solution of the Schr?dinger equation complicated. An additional complication is that electrons in the vicinity of heavy atomic nuclei move close to the speed of light. When such atoms are present, we must solve Dirac’s relativistic equation rather than the non-relativistic Schr?dinger equation. In fact, even some enzymatic processes in our bodies are incorrectly described by the Schr?dinger equation, needing a relativistic treatment of the electrons for a correct description.
- Near heavy metal nuclei (which are also found in our bodies), electrons move at speeds close to that of light. You will then get the wrong answer if you ignore relativity.
All this fascinating number crunching has resulted in the recruitment of additional researchers and an engineer. The Hylleraas Centre has thus been strengthened, with a stronger leaning towards biology – a strategic choice for the future, emphasizes Helgaker.
Read more about the six research topics and the researchers:
Electronic Structure, by Thomas Bondo Pedersen
Multiscale modelling, by Michele Cascella
Spectroscopic processes, by Thomas Bondo Pedersen
Extreme environments, by Trygve Helgeaker