I remember sitting through an interminable inorganic chemistry lecture as an undergraduate, frantically scribbling notes and wondering whether everything was basically word-for-word in the textbook as it had been in the previous week's burst of information. At some point, the lecturer tossed in the word relativity with sheer abandon as if it were an everyday concept to hear in a chemistry lecture. I was at the time doing a joint honors course with physics and so was used to hearing stuff about relativity and almost ignoring it in lectures elsewhere on campus. But, this was chemistry...this was 1985, what did Einstein have to do with inorganic? Schrodinger, yes, of course, quantum mechanics, Hamiltonians, etc, but relativity?
Well, apparently so, there was more overlap at the electron level between my undergraduate chemistry and physics courses than I'd assumed there would be. Turned out that the velocity of the electrons in the orbitals of the complex under discussion were a reasonable fraction of the speed of light and as such relativistic effects had to be taken into account when modeling its structure, to explain the properties, the energy levels and the structure of the complex. Of course, more than thirty years later, I cannot recall exactly what this structure was. But, I do vaguely remember that the fact that gold looks "yellow", as opposed to silvery is due to a relativist effect. It is biased towards the absorption of blue light it seems, a similar effect is observed with cesium. Copper is different, just conventional energy level effects giving rise to its ruddy hue and osmium's bluish hue. Moreover, a relativistic effect also precludes mercury from forming strong Hg-Hg bonds and it remains a liquid metal at room temperature and, indeed, down to a chilly -39 degrees Celsius.
It still seems rather fascinating to me that there exist bridges between the physical sciences that span the sub-atomic and all the way through to the cosmic in this sense, despite the fact that we are yet to reconcile gravity and quantum mechanics in a single theory. Some scientists have been making waves recently in that particular field, of course, but nothing sticks yet.
Meanwhile, a research paper came my way about which I intended to write a short news story that brought this overlap to my attention once more. The work pertained to a simple-looking compound that theory suggested would exist in a stable state under only very narrow and specific conditions. Moreover, its stability would only be sufficient if the theoretical calculations accommodated relativistic effects. This seemed like news to me. However, things have apparently moved on in 30+ years. At least this was the impression I got on interviewing the researchers and one independent witness none of whom were particularly hyped by the notion of relativity being important in this science. It turns out that relativistic effects are a "common or garden" feature of chemical computation these days and so my news hook about the chemical Einstein seemed not so bizarre as I had first thought. However, to other chemists with whom I spoke, not least my editor, the mash-up between chemistry and physics in this system was news. As such we settled on something of a compromise that drew attention to the Einstein angle without implying that nobody had spotted it before. Of course, they had, but it is still intriguing, isn't it, relatively speaking?
It was British physicist Bertha Swirles, Lady Jeffreys (22 May 1903 - 18 December 1999) of the University of Cambridge, who began work on a relativistic treatment of a many-electron system in 1935. However, Paul Dirac had already asserted that in the quantum world relativistic effects would be negligible, so who was she to argue in a scientific world dominated by men? It wasn't until the 1970s that "corrections" to Schrödinger's equation were first taken seriously by others because of the realization that electrons could be moving at high speeds and so spectra would be affected and Lady Jeffreys' treatment was vindicated. Nevertheless, this seemingly obscure loop of physics only slowly entangled the chemical consciousness though, in dusty lecture theatres in dusty undergraduate memory. It seems to this day that it still remains fairly obscure, perhaps with the exception of those whose disciplines span both chemistry and physics.
David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".