Monday, 7 May 2012

Journal Club: A New Blog

I've just started a new blog It's definitely in what you'd call the beta phase right now. I will certainly be changing the layout and gradually adding more permanent content over the next few weeks.

Contributions welcome to

While I do sometimes get a bit technical, Kinetically Constrained is hopefully of interest to people inside and outside of the field. The idea for the journal club is that it is aimed at people working in the area of soft matter and statistical mechanics. In particular I want it to be useful for postgraduate students who would find it helpful understanding papers they may have found a bit impenetrable otherwise.

How it will all work will hopefully evolve. I hope one day enough people check it out that the following scenario happens. A PG student presents a paper as best they can that they might be having trouble understanding. A comment thread follows and the problems get sorted out. Everyone wins.

I also suspect that hundreds of journal clubs happen each week in different universities. While I understand people might not want this to be public, for those that don't mind they could put their presentation on SCM journal club where it can benefit even more people.

To kick things off I've started with a recent paper on the arXiv by AndrĂ©s Santos on one of my favourite topics – hard spheres.
Brief Summary
In liquid-state theory the hard sphere equation of state is of particular importance because it is a fantastic reference system for a whole host of molecular and in particular colloidal liquids. The hard sphere equation of state (EoS) tells you what pressure you need to compress a your spheres to get a given density. With an analytical form for the EoS one can calculate any thermodynamic property one desires.
Percus-Yevick (PY) is a way to close to the Ornstein-Zernicke (OZ) equation – an exact relation between correlation functions – and is usually solved by either the compressibility route or the virial route. You’re basically choosing how your approximation enters. Here Santos has taken a different route, following the chemical potential, and it gives a slightly different closure to OZ.
Carnahan-Starling is an incredibly simple EoS for hard spheres which is in common use (fluid phase). It can be written as a 1/3-2/3 mix of the compressibility and virial PY routes. In a similar way Santos writes a 2/5-3/5 mix of compressibility and chemical potential routes and gets a similarly simple expression – which is ever-so-slightly better than Carnahan-Starling.
I'm more than happy to take contributions. I think it's nicer if people say who they are but I'll hold back the name if that's the barrier to submitting (provided it's not an anonymous destruction of a rival's paper). You can submit via For interested regulars I can look into direct posting via blogger.