Professor Graham Worth delivered his inaugural lecture as a newly appointed Professor in September 2015. This series celebrates his success in the field of Theoretical Chemistry.

Professor Graham Worth’s ‘big breakthrough’ moment came 16 years ago. Today, however, he remains as passionate and determined as ever to push the boundaries of scientific knowledge further still. 

Graham, a Professor in Theoretical Chemistry, was at the University of Heidelberg, on a Marie Curie Fellowship, when in 1999 he published his seminal paper on the then-novel Multi-Configuration Time-Dependent Hartree (MCTDH) method for molecular systems – a general algorithm to solve the time-dependent Schrödinger equation, which is the fundamental equation of physics for describing quantum mechanical behaviour.

The computer program Graham developed is now used by many research groups around the world and provides the benchmark against which other methods are tested.

For me, the end result is always about what can you calculate. Even after all this time, we are still putting the tools together to solve real-life problems.

‘Since then we have been developing both the code and the method further, to make it more general, easier to use and more efficient,’ he says.

Graham, who has been at Birmingham for a decade and recently delivered his Inaugural Lecture, coordinates further developments of the program in collaboration with groups in Europe, Canada and Australia. He also chairs the Collaborative Computational Project on Molecular Quantum Dynamics.

The way we describe how molecules behave has been Graham’s main interest since his undergraduate days at Oxford.

‘A lot of chemists like making things, but right back when I was doing my undergraduate degree, describing the behaviour of molecules was the part I was interested in,’ he explains. ‘This was the time when computational chemistry was starting to take off: for the first time, computers were powerful enough to do calculations. We had the codes and computational resources to calculate and compare in a way that hadn’t been possible before; it provided a way to give a language to things that chemists measure and observe.’

Graham’s initial calculations were simple models in biological systems, such as antihistamines. Then he moved on to look at more fundamental theory.

‘I wanted to understand how the simple models we were using worked in the way that they do (in chemistry we use a lot of models). I wanted to know how very simple models – all based on molecules as balls and springs – fitted in with really fundamental theory of quantum mechanics, describing matter in waves.’

Soon, Graham was immersed in the field of quantum dynamics: applying the full quantum theory to molecular behaviour.

In 1992, he was offered a postdoctoral position at the European Molecular Biology Laboratory in Heidelberg, Germany, to study protein dynamics. Two years later he moved to the University of Heidelberg, switching to the field of accurate quantum dynamics studies of small molecules and the development of the MCTDH program.

‘The MCTDH was developed by two colleagues there and I wrote the program that implemented it,’ explains Graham. ‘At the time, we could only look at three or four atoms at a time, but the development of the MCTDH enabled us to look at ten. That was a huge jump.

‘Our big breakthrough paper came in 1999, where we did the calculation of the absorption spectrum for a 10-atom molecule. This is what you see if you shine light through something. We calculated it to be pretty much the same as the measurement. That is still the benchmark today against which many researchers compare their own methods.’

In the proceeding 16 years, Graham has been working to further develop the code and the method.

‘The algorithm has been developed not just by me, but also by others, and it can now do much larger systems,’ he explains. ‘It’s been used to study a whole range of systems, such as semi-conductors and photo-activated processes – how molecules behave when they have absorbed light, which is something I’m particularly interested in and which has a range of possible applications, such as solar energy, organic LEDs, stability of DNA, and sunscreen. You can also use it to study the rates of reactions for atmospheric chemistry, which is necessary in order to know how fast molecules react when they collide.’

Graham, who is recognised internationally for his studies of ultrafast photochemistry and non-adiabatic effects, is currently involved in two three-year, collaborative projects.

One of those is working with Professor Mike Bearpark from Imperial College, London on developing a code for photo-activated molecules; the other is working with Professor Helen Fielding, also from Imperial, on building new technologies to look at molecules in solution.

‘Up until now, everything we’ve looked at has been in the gas phase. This work will help us see how important it is when something is surrounded by water.’

Graham’s enthusiasm for pure science remains undimmed. ‘For me, the end result is always about what can you calculate. Even after all this time, we are still putting the tools together to solve real-life problems.’