Relativity—it’s everywhere. Observers of the Aurora Borealis are witnessing a union between quantum theory and the theory of relativity. Visscher uses this image as a visible example of relativistic effects in atoms. Image courtesy of the University Corporation for Atmospheric Research

If you’ve visited Helsinki or Anchorage, you may have seen visible proof of Einstein’s theory of special relativity: the red color in the Aurora Borealis.

The atoms forming our atmosphere—mostly oxygen and nitrogen—don’t move fast enough to display relativistic effects, but lightweight particles in these atoms—the electrons—do.
   
“Electrons can move at about 10% the speed of light,” says Lucas Visscher, theoretical chemist at Vrije University Amsterdam in the Netherlands. “At this speed we begin to see noticeable effects of relativity.”

These effects come about because electrons spin as they orbit their atom’s nucleus—like the earth rotates as it orbits the sun.

In a non-relativistic world, these movements would be independent. But in our relativistic world, the orbit and rotation are coupled.

“Relativity allows for a flip in the electron’s spin,” says Visscher. This flip, he says, gives rise to one of the hallmarks of the Aurora Borealis: “In a non-relativistic world we would never see the long-lasting red phosphorescent effect.”

Visscher uses these principles of relativity to study and predict the behavior of atoms and molecules, developing complex computer models to describe the structure and dynamics of chemical bonding.

Left: traditional (non-relativistic) picture of the astatine orbitals; right : a relativistic view, the direction of electron spin depends on its position in space. Visscher is developing grid-enabled software to better predict the structure and dynamics of such molecules. Image courtesy of Lucas Visscher, Vrije University Amsterdam

For small molecules, like oxygen or astatine, models that account for relativistic effects can be more precise than our most accurate experimental measurements.

Visscher and his colleagues want to expand this accuracy to encompass larger molecules, and in the distance is a molecular holy grail:

“Ideally we would like to be able to design molecules and build them. Architects and engineers, knowing the laws of physics, can construct buildings. We would like to do the same with molecules.”

In his work Visscher uses computing resources distributed across four universities. His software runs on three middleware systems: Gridlab, UNICORE and Xgrid.

Currently, Visscher and his team are developing a model that will combine two molecular modeling software packages, each containing 100,000 lines of code.

When completed, this model will integrate density functional theory and wave function theory. Density functional theory explains the distribution of electrons in molecules and allows the prediction of most physical properties; wave function theory does the same thing, only more accurately, including more variables, and costing ten times more to run. Once working, their model will give a more accurate and less expensive tool for studying larger molecules.

“I’m interested in creating the software for this,” says Visscher. “I’m happy to then turn it over to other researchers to help them with their work.” 

- Danielle Venton, iSGTW