Condensed concepts

Roald Hoffmann and Jean-Paul Malrieu are two of my favourite living theoretical chemists. Both greatly value the role of concepts and intellectual clarity in theory. Hoffmann has featured in 22 posts on this blog. They recently published a wonderful trilogy in  Angewandte Chemie. Simulation vs. Understanding: A Tension, in Quantum Chemistry and Beyond.  Part A. Stage Setting Part B. The March of Simulation, for Better or Worse Part C. Toward Consilience I add this trilogy to my list of 5 papers every computational chemistry student should read , suggested by me a decade ago. [Malrieu is author of one of those and Hoffmann co-author of another.] Although the trilogy addresses and uses specific examples from computational quantum chemistry it is just as relevant to anyone interested in computational materials science. Actually, I hope that anyone interested in materials science would read and digest it as it gives a sober and balanced perspective about the relationship between theory, si

  Covid-19 has turned the world upside down. Different people and communities have had very different experiences. In my state of Queensland, it is almost a different world. To illustrate I share the data above, which prompted a three-day lockdown in Brisbane. For reference, Queensland has a population of 5.2 million. A number of factors have contributed to the relatively positive situation. Australia is an island. Our borders were closed early. There was unity between state and federal governments. Generally, lockdowns have been pronounced promptly. Although Australians do not like authority and are a rebellious bunch, lockdowns and mask mandates have generally been observed. We are not immune from conspiracy theories and vaccine hesitancy. But, overall we have not been plagued by the same level of "politicisation" that has hobbled other countries.  In some ways, I feel I am living in a different world. Yet, some of this good fortune should not lead to pride and complacency.

Condensed matter physics is about the properties of real materials. Real stuff that you can see and touch and that you can use to make very practical things like TV screens and mobile phones. Yet, I find it fascinating and somewhat ironic that in condensed matter theory very abstract ideas and mathematical techniques keep cropping up (and being extremely useful): variable spatial dimensions, imaginary frequencies, topology, Chern numbers, conformal invariance, ... Yet, there is a danger with abstraction. Theoretical condensed matter is not pure mathematics. Perhaps, too often fancy and beautiful mathematics is prized over physical intuition and insight. Theory may take precedence over experiment. How does one find the appropriate balance? This is part of broader issues about the role of abstraction and formality in education. Pierre de Gennes (1932-2007) was arguably the founder of soft matter as a research field, as recognized by the Nobel Prize in Physics in 1991. He began his care

This week my wife and I did some science experiments with kids, aged about 8-12, at a holiday kids club organised by our church. The first day we did rockets, using the old standbys of baking soda rockets and mentos and coke. On the second day, we did the science of chocolate. Ten years ago (!) we had done this based on some demonstrations developed at Harvard, described in this paper  The Science of Chocolate: Interactive Activities on Phase Transitions, Emulsification, and Nucleation .  Teaching kids about phase transitions with ice and steam is not quite as exciting or memorable as them melting chocolate in their mouths. An important scientific idea is: Physical properties of matter (such as melting temperature) change with differences in chemical composition. This is illustrated by the different melting temperatures of white, milk, and dark chocolate. We also tried to mix water and oil, with and without the presence of detergent. This illustrates ideas about emulsification, includ