Springer LINK: The European Physical Journal B - Abstract Volume 5 Issue 3 (1998) pp 825-833

The European Physical Journal B

ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)

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Abstract Volume 5 Issue 3 (1998) pp 825-833

Competing bulk and surface fields in d=2 Ising films near bulk criticality: effects of fluctuations

A. Drzewinski (1) (a), A. Ciach (2), A. Maciolek (2)

(1) Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, Wrocl aw 2, Poland
(2) Institute of Physical Chemistry, Polish Academy of Sciences, Department III, Kasprzaka 44/52, 01-224 Warsaw, Poland

Received: 11 February 1998 / Received in final form: 16 February 1998 / Accepted: 17 March 1998

Abstract: The two-dimensional Ising films $L \times \infty$with bulk H and surface H₁ fields of opposite sign are studied above and close to bulk criticality by the density matrix renormalization group method. This technique, applied recently to d=2 Ising films, allows for very accurate results for the adsorption $\Gamma$ as a function of the reduced deviation from the critical temperature $\tau$.For strong H₁ three distinct classes of shapes of $\Gamma(\tau)$,determined by the value of the parameter $\tau_H \sim (\vert H\vert L)^{1/(\Delta-\nu)}$,where L is the width of the film, are found in agreement with earlier predictions [A. Macio\l ek, A. Ciach, R. Evans, J. Chem. Phys. 108, 9765 (1998)]. For strong and for weak bulk fields $\Gamma(\tau)$ is a monotonic function, increasing for strong H and decreasing for weak H, in agreement with scaling analysis and earlier mean-field results. For H between these extreme cases $\Gamma(\tau)$ assumes a maximum for $\tau\sim\tau_H$ and for $\tau < \tau _H$ a depletion occurs, as in recent experiments for critical adsorption in porous materials. For a limited range of H a qualitatively new behavior of $\Gamma(\tau)$ is found. In addition to a maximum, a minimum of $\Gamma(\tau)$ for $\tau\sim L^{-1/\nu}<\tau_H$ appears, which in the mean-field analysis was absent.

PACS. 05.50+q Lattice theory and statistics; Ising problems[:AND:] 05.70.Jk Critical point phenomena

(a) email: drzewin@apollo.int.pan.wroc.pl

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