Category Archives: science

Advances in computational and experimental studies of solids: a meeting to mark Richard Catlow’s 70th birthday (Cosener’s House, Abingdon, 10-12 April 2017)

It was back in March 2016 that I first had the idea that a meeting should be arranged to mark Richard Catlow’s 70th birthday. Having organised a similar occasion for his 60th birthday, back in 2007 (unfortunately pre-blog and my use of social media), this seemed appropriate. Initially the idea was to have an organising committee, and I approached potential members, but it soon became clear that it could only be done effectively by close liaison with Richard, and from then on I was effectively the sole organiser (although I am grateful for administrative help received later).

We discussed possible dates in April 2017, and where it could be held. Richard preferred a neutral venue not associated with his current employers, so eventually we settled on Cosener’s House, a place in Abingdon often used by people carrying out experiments at the nearby Rutherford Appleton Laboratory. The venue was booked, and all available rooms were reserved, and we set about discussing who should be invited, before the event was advertised more widely. I made a list of Richard’s contemporaries who he particularly wanted to attend, and invited them. It was very encouraging that they all accepted. I then advertised the meeting to pre4sent and former group members, inviting them to register and present talks.

In September 2016 I met with Richard to discuss the general format of the meeting, and in February 2017 we started putting the programme together. All this coincided with my appointment as acting head of my school at Keele, and having two new modules to teach, so it was difficult for a couple of months. But by mid March everything was coming together. Ideally I would have liked a site visit, but there simply wasn’t time.  However, I had discussed everything in detail with both Richard and the Cosener’s House staff, so I hoped everything was in place!

On Sunday 9th April (2 weeks ago from writing this post), I set off to Oxford, staying overnight close to the station, and on Monday 10th April I took a taxi to Abingdon, arriving at Cosener’s House a few hours before the meeting was due to take place.

I’m pleased to say that the meeting got off to a great start. It was particularly pleasing to get so many of Richard’s former group members together, as well as people he had worked with, including Sir John Meurig Thomas, Tony Cheetham and Brian Fender. We even had a visit from Richard’s PhD supervisor, Alan Lidiard. The talks were excellent, and we had lots of good discussion. The accommodation and catering were both excellent.

All in all I was very pleased with the meeting, and pleased that everyone enjoyed it. You can find a collection of photos taken at the meeting here: https://www.flickr.com/photos/robajackson/albums/72157680516575331, and one of the conference photos is given below. I will also post the meeting programme on my website (www.robajackson.com) in due course.

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Statistical Thermodynamics Lecture 3, and the Sackur-Tetrode equation centenary

My third statistical thermodynamics lecture took place last Thursday afternoon. The timetable didn’t help; it was the second lecture in a double slot, and I think that a subject as conceptually and mathematically difficult as statistical thermodynamics can only be digested in limited chunks! But in spite of that, it seemed to go OK.

As for what was covered, I started with calculation of the Gibbs energy for monatomic and diatomic gases. The problem with this, as I commented last year, is that it doesn’t give a value which can be experimentally verified (you would have to calculate the values for each species in a reaction and then obtain the change in Gibbs energy to be able to do this). But nevertheless, it’s very useful to be able to do this type of calculation.

Moving on, I covered the relationship between equilibria and the Boltzmann distribution. This is really interesting, especially where it ties in with the role of entropy in the thermodynamics of reactions. I use a pictorial approach, taking inspiration from Atkins & de Paula, Elements of Physical Chemistry. This leads to the relationship between the  equilibrium constant and the partition functions of the reactants and products. I agree with Profs. Atkins and de Paula that this is a quite extraordinary equation, relating macroscopic and microscopic thermodynamics. I illustrate the use of this equation for an ionisation reaction, as is done in several of the textbooks.

In closing, I should mention (as I did in a tweet last week), that the Sackur-Tetrode equation is 100 years old this year. This is another amazing equation, which enables entropies to be calculated with impressive accuracy, using only some constants and atomic masses. It was derived independently by Sackur and Tetrode, with Hugo Tetrode being a scientist from the Netherlands who carried out some very important work but died at the age of 35. His profile was such that he was once visited by Einstein and Ehrenfest, but they were turned away by his housekeeper! In my tweet I gave a link to a paper about the derivation of the equation.

My next teaching challenge, starting later this week, is four lectures on ballistics for our final year forensics students. Quite a contrast in topic!

Statistical Thermodynamics Lectures 1 and 2

I’m giving my Statistical Thermodynamics Lectures this week. I have about 3.5 hours, which includes a double slot on Thursday. I hate double slots, and I suspect the students do too, but that’s another subject!

So, as with the Quantum Chemistry, it comes down to deciding what to cover and in how much detail. I start by trying to explain the importance of the subject – bridging the macroscopic and microscopic strands of Physical Chemistry, enabling the calculation of thermodynamic quantities etc. To be honest, I don’t know how much of an impact that statement makes to the students, because until you’ve seen the ‘bigger picture’ it’s hard to see the subject in this way. But I think it’s important, otherwise the subject is in danger as being viewed as ‘just a collection of equations’.

In the first lecture I start with the Boltzmann Distribution, which has been covered before, so hopefully it’s revision. That takes me straight into partition functions, and I try to eplain why they are useful and what information they give. I suspect if the person who taught this subject to me had done this at the time, it might have made more impact! I then go through translational, rotational and vibrational partition functions and give examples of calculations. Last year there were issues with units, and confusion between wavenumber and frequency, so I’ll spend a bit of time on that.

Lecture two is about using Statistical Thermodynamics to calculate thermodynamic properties. Starting with internal energy, we consider heat capacity, residual entropy, and finally entropy itself, using the Sackur-Tetrode equation, that celebrates its centenary this year. Heat capacity and residual entropy are good examples because there are experimental values to compare with. I show some example calculations, and try to stress that these have to be done in stages, because calculators can’t cope with the magnitude of some of the numbers involved.

I’ll consider lecture 3 in a separate post. It will need some thought for this year, because some of the material I’ve covered previously didn’t go down too well last year. Thankfully I have some time to sort this out!

Quantum Chemistry in 3 lectures: lecture 3

So lectures 1 and 2 took place last week, and seemed to be received reasonably well. Lecture 3 is scheduled for Tuesday morning. In this lecture I introduce the Schrodinger equation and the Hamiltonian operator, and talk about how the equation is solved for the particle in a box, the harmonic oscillator, and the hydrogen atom. Because the class have mixed experience of maths, I try to keep the maths content to a minimum, and instead stress concepts. This seems to work OK for the first two examples, but it’s hard to do convincingly for the hydrogen atom. The bit that seems to make sense even without detailed maths is where the wavfunction is split into radial and angular dependent parts, and interpreted in terms of the different orbitals. But at least the lecture seems to tell a coherent story! I’ll discuss more in the next post, when I’ll also descibe my preparations for the statistical thermodynamics lectures.

‘How To Teach Quantum Physics To Your Dog’, by Chad Orzel

I picked up this book at the W H Smith shop on Reading Railway Station about 3 weeks ago. At the time I was thinking about my upcoming Quantum Chemistry lectures, and as usual, looking for some inspiration to add some new material or find a different approach some aspects of the subject. This book has certainly helped me on both counts.

First, some basics. You can read about the book here, and the author has a blog, which is worth following. He is also on Twitter, as @orzelc. If you’re reading this in the UK, you can order the book from Amazon for £5.11 (at the time of writing).

The book starts with a discussion of why you would want to discuss quantum physics with your dog, and makes the interesting point that one of the reasons why we as humans sometimes find the results of quantum theory confusing is that we are conditioned by ‘classical’ results. Dogs, however, do not have any pre-conceptions, so they will not have this problem. An introduction to quantum physics then follows.

The book has 10 chapters, each dealing with a specific topic, such as wave-particle duality and the Heisenberg uncertainty principle, and each chapter is a combination of an explanation of the subject and a conversation between the author and his dog, Emmy. It has to be said that Emmy is no ordinary dog, and she learns quickly, as well as reading the author’s books when she is alone in the house! Each topic is explained very clearly and without too much jargon or unnecessary teachnical terms.

The book is a refreshing take on quantum physics, and I found that it gave me some new ideas for my teaching, as well as teaching me some new things which I hadn’t encountered before. These included the extension of electron diffraction to the diffraction of molecules, including ones as heavy as C60. This has now got into my lectures, duly acknowledged, of course!

I definitely recommend this book for anyone interested in quantum physics/quantum mechanics, whether it’s a general interest or a professional one. And if you are interested in Relativity, Chad’s new book, How To Teach Relativity To Your Dog, is now available for pre-order from Amazon.

Quantum Chemistry in 3 lectures: lectures 1 and 2

This is the time of the year when I teach Quantum Chemistry and Statistical Thermodynamics to our second year class. I have 3.5 lectures for each, but usually do 3 lectures for each topic and use the extra lecture as a class problems session.

In this post I will concentrate on the challenge of fitting the important parts of Quantum Chemistry into 3 lectures, and will consider the first 2 of these lectures specifically. The third lecture will then be covered in a separate post.

So the first consideration is: what topics to cover? Most textbooks start their treatment of Quantum Mechanics with a discussion of the experiments whose analysis ultimately led to the development of the subject, and I have followed this path too. So Lectures 1 and 2 are really about the experiments that established the ideas of wave-particle duality, and in lecture 1 I consider the experiments that showed light to have particle properties, i.e. the Photoelectric Effect and the Compton Effect. Both experiments are described in detail, but this year I am hoping to include some video clips, where the experiments are actually demonstrated. Links to some selected clips will be added to my Facebook teaching pages, so anyone interested can easily find them and try them out themselves. For both the Photoelectric Effect and the Compton Effect I have included descriptions of experimental methods that have been developed based on them, namely Photoelectron Spectroscopy and the Compton Telescope. The aim here is to show that as well as helping to develop a new subject area, the experiments gave rise to useful methods for Chemistry and Gamma Ray Astronomy respectively.

So, in summary, lecture 1 confirms the ideas of photons and justifies the Planck relation for energy and frequency (E = hf). The students will have already met this in other modules, but to truly understand it, you need to look at the results of something like the Photoelectric Effect experiment.

Lecture 2 starts with the idea of wave-particle duality, and the de Broglie equation. The impressive thing about de Broglie’s work is that he predicted the wave properties of particles before they were demonstrated unequivocally in the Electron Diffraction experiment. I will describe Electron Diffraction, again hopefully including some video clips. I am also going to discuss whether diffraction is possible with larger ‘particles’, including C60 molecules. I got this idea from Chad Orzel’s excellent book ‘How To Teach Quantum Physics To Your Dog‘, which I have read recently, and which has been a great source of ideas for these lectures.

Having discussed the Electron Diffraction experiment, and reached the conclusion that the electron shows wave behaviour, it’s time to introduce the idea of wavefunctions. The students are already familiar with the idea of orbitals, but for the first time they will get a proper explanation of why they are used. So I introduce orbitals first, and use them to bring in wavefunctions. The idea of a wavefunction is a difficult one, but I hope that using orbitals as an illustration will help. The idea is that by the end of lecture 2 we know about orbitals, so that the calculation of wavefunctions by the Schrodinger equation can be introduced smoothly at the start of lecture 3!

If you would like to have a look at the lecture slides for this course, you can find them here.

Lecture 3 will be described in a post next week. I will also mention any good or bad points from lectures 1 and 2 for future reference.