Measuring the equation of state of a hard-disc fluid

M. Brunner; C. Bechinger; U. Herz; H. H. von Grünberg

doi:doi:10.1209/epl/i2003-00495-1

DOI: 10.1209/epl/i2003-00495-1
Europhys. Lett., 63 (6) , pp. 791-797 (2003)

Measuring the equation of state of a hard-disc fluid

M. Brunner, C. Bechinger, U. Herz and H. H. von Grünberg

Universität Konstanz, Fachbereich Physik - D-78457 Konstanz, Germany

(Received 28 May 2003; accepted in final form 8 July 2003)

Abstract
We use video microscopy to study a two-dimensional (2D) model fluid of charged colloidal particles suspended in water and compute the pressure from the measured particle configurations. Direct experimental control over the particle density by means of optical tweezers allows the precise measurement of pressure as a function of density. We compare our data with theoretical predictions for the equation of state, the pair-correlation function and the compressibility of a hard-disc fluid and find good agreement, both for the fluid and the solid phase. In particular, the location of the transition point agrees well with results from Monte Carlo simulations.