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Physical Chemistry

Strong Paramagnetism Makes Strong Bonds

Computations predict a distinct new form of chemical bonding in exotic astronomical environments

by Elizabeth K. Wilson
July 23, 2012 | A version of this story appeared in Volume 90, Issue 30

Extremely strong magnetic fields, such as those found around dense astronomical bodies like white dwarfs and neutron stars, could create a third form of chemical bonding quite different from covalent or ionic bonding, physicists report (Science, DOI: 10.1126/science.1219703). In the past, theoreticians have proposed that a magnetic field thousands of times stronger than that achievable in a laboratory could fundamentally alter chemical bonding. But until now computations have not been sophisticated enough to make reliable predictions. Trygve U. Helgaker of the University of Oslo and colleagues developed software that they say can accurately describe molecules at all orientations in a strong magnetic field. They used the program to model the binding properties of H2 and He2 in magnetic fields up to 100,000 tesla; the strongest man-made magnets are about 40 tesla. Their computations predict that when the diatomic molecules are positioned perpendicular to an external magnetic field, antibonding orbitals in the molecules are stabilized. This leads to a strong paramagnetic bonding of the atoms that would otherwise fall apart. The finding has added a key new mechanism to the “fascinating topic” of bonding, writes the University of Hamburg’s Peter Schmelcher in an accompanying perspective.


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