Synopsis: Golden Mystery Solved

A long-standing discrepancy between experiments and theory concerning the electronic properties of gold has now been resolved.

Gold’s lustrous color is due to unusually strong relativistic effects. The same effects also complicate theoretical computations of gold’s electronic properties. Indeed, theorists working on this precious metal have struggled for decades to resolve a discrepancy between their predictions and experimental observations. New work has solved this problem by calculating the electron correlation contribution to an unprecedented level of precision that incorporates “pentuple” interactions between five electrons.

Calculating an atom’s electronic properties is never easy, especially for heavy atoms whose strong Coulomb potential implies relativistic energies for its electrons. In gold’s case, relativistic effects cause a smaller than expected gap between the 6s and 5d orbitals, which is why gold absorbs blue frequencies and reflects a yellowish tint. But other aspects of gold are more difficult to explain. Calculations of the ionization energy (energy to remove an electron) and electron affinity (energy to add an electron) have consistently underestimated the experimental values by tens of milli-electron-volts.

Peter Schwerdtfeger from Massey University Auckland in New Zealand and his colleagues have performed precise calculations for gold. Their model accounts for relativistic effects, as well as for the contributions from electron correlations and quantum electrodynamics. Electron correlations embody all the electron-electron interactions that occur in a multielectron atom. Previous studies have dealt with electron correlations between the 79 electrons in gold, but typically they have only gone as far as triple interactions between three electrons. Schwerdtfeger’s team extended these calculations to quadruple and pentuple interactions. By doing so, they reduced the discrepancy in the ionization energy and electron affinity to just a few milli-electron-volts —a factor of 10 improvement over past results. The methodology could be applied to even heavier elements.

This research is published in Physical Review Letters.

–Michael Schirber

Michael Schirber is a Corresponding Editor for Physics based in Lyon, France.


More Features »


More Announcements »

Subject Areas

Materials Science

Previous Synopsis


Flip-Flopping the Bands

Read More »

Next Synopsis

Nonlinear Dynamics

Chaos from a Chilled Cloud of Atoms

Read More »

Related Articles

Focus: Ultrafast Switch with Organic Crystal
Condensed Matter Physics

Focus: Ultrafast Switch with Organic Crystal

An organic crystal was switched between paraelectric and ferroelectric states in a picosecond. Similar materials could eventually serve as extremely fast digital switches. Read More »

Synopsis: Dirac Cones in Boron’s Version of Graphene
Materials Science

Synopsis: Dirac Cones in Boron’s Version of Graphene

A one-atom-thick sheet of boron atoms exhibits Dirac cones, marking the first time this electronic property has been found in a material lacking a graphene-like crystal structure.  Read More »

More Articles