Ian Ford

statistical physics nucleation of phase transitions aerosol physics molecular dynamics in condensed matter physics Contact details: Office: Room E2 Physics Tel: +44 (0)20 7679 7136 Ext: 37136 Fax: +44 (0)20 7679 0595 Email: i.forducl.ac.uk

The atmosphere is loaded with tiny suspended particles called aerosol, ranging in size from nanometres to micrometres, and consisting of a great variety of materials. My research centres on understanding the origins of these particles. Many are formed by condensation of gas phase precursors, by a process called nucleation. Each particle starts out as a cluster of molecules, and the stability of these clusters is key to their rate of formation. However, this stability defies all textbook material properties, since the clusters are so small. Developing  theoretical models of clusters is therefore key to making progress.

My theoretical work on the nucleation of phase transitions applies to other areas too, including protein aggregation, biomolecular structural changes, colloidal crystallisation and stock market dynamics. I also take an interest in the fundamental nature of irreversible processes, of which nucleation is an example., and in general aerosol physics.

I teach a course on stochastic dynamics to third year undergraduates. This area of mathematics is applied widely in the area of statistical physics, for example to describe the Brownian motion of colloidal particles, and the effects of thermal fluctuations on molecular structures. More recently, it has been used to model the random evolution of share prices.

I am the Undergraduate Physics Programme Tutor, and organise the delivery of teaching to over 200 students in the Department of Physics and Astronomy.

I am President of the Aerosol Society, a learned society which aims to promote research in the field of aerosol science in the UK and Ireland.

Recent Publications

I.J. Ford and S.A. Harris, “Molecular cluster decay viewed as escape from a potential of mean force”, J. Chem. Phys. 120 (2004) 4428-4440.  download
This paper develops a model of evaporation from molecular clusters using stochastic dynamics and the concept of the cluster potential of mean force.

 I.J. Ford, “Statistical mechanics of nucleation: a review”, Proc. Instn Mech. Engrs 218 Part C: J. Mech. Eng. Sci. (2004) 883-899. download
This is a general review of the current state of nucleation theory, with particular reference to the condensation of steam in power turbines.

S. Khakshouri and I.J. Ford, “Thermodynamics of attractive hard rods: a test of mean field density functional theory”, J. Chem. Phys. 121 (2004) 5081-5090. download
This is a test of the accuracy of a standard theory of liquid-like molecular clusters. If the model works well for a simple one-dimensional system with just two interacting constituents (which it does, with some modifications) then it should work well for larger clusters in three dimensions.

• BA Physics and Theoretical Physics, Cambridge 1984
• DPhil Theoretical Particle Physics, Oxford 1988
• Theoretical Physics Division, Harwell Laboratory, UKAEA 1987-1995
• Department of Physics and Astronomy, UCL, 1996-present

 A cluster of 67 molecules of nonane, a substance similar to the octane found in petrol, is glimpsed in a computer simulation just after the loss of one of its constituents. The colours are artificial and serve to distinguish the molecules. We can measure the lifetime for such an evaporation event at room temperature to be several tens of nanoseconds. This is very fleeting indeed, but not so short as to make it improbable that a molecule from the surrounding vapour might stick to the cluster first. It is only by such random growth of clusters by condensation, against the natural tendency for the cluster to evaporate, that fresh particles are formed in the atmosphere, in a process known as nucleation.