Shift of the Critical Mixing Temperature in Strong Electric Fields. Theory and Experiment

Abstract

We study the shift in the critical temperature T(c) in binary mixtures in strong electric fields. In experiments we measure the nonlinear dielectric effect (NDE) in a mixture of nitrobenze and n-octane and calculate Piekara's factor. We find that the critical anomaly of Piekara's factor is a function of an electric field strength. We propose to explain this observation as a result of a downward shift of T(c), and this allows us to calculate (∂T(c)/∂E(2)) = (-22 ± 10) × 10(-16) (K m(2))/V(2). In the theoretical part we amend Landau and Lifshitz's formula and show that the downward shift of Tc can be estimated from a simple mean-field theory taking into account the linear and quadratic terms in an expansion of the constitutive relation ε(x) between the electric constant ε and mixture composition x.

Liquid-vapor interface of the Stockmayer fluid in a uniform external field

“…The presence of an external field brings an additional control that can be used to switch or modify the statistical states of the fluid. Liquid-vapor coexistence is a key aspect of the phase diagram of any liquid, and there has been much interest in liquid-vapor coexistence in dipolar systems in an external field both experimentally [2][3][4][5][6] and theoretically [5,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…Several experiments have found that the presence of an electric field leads to a decrease in critical temperature of binary mixtures [2,3,5]. Beaglehole found the change in critical temperature for a mixture of cyclohexane/aniline depends on the field direction; the critical temperature increases for the field perpendicular to the interface, and decreases with field parallel to the interface [4].…”

“…density for a pure fluid), which for most fluids is positive [8]. This leads to an increase of critical temperature for constant surface potential [5]. Stepanow and Thurn-Albrecht formulated a statistical mechanical description of liquid systems for polar systems in an electric field with constant potential boundary conditions and also found that the field induced a postive shift of the critical temperature for polar liquids [10].…”

The super- and sub-critical effects for dielectric constant in diethyl ether

“…16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] This can be associated with the fact that generally for critical mixtures dT C /dE 2 < 0. 53 The only exception, still not explained ultimately, was obtained in nitromethane -3-pentanol critical mixture. 17 In the opinion of the authors the increase of the critical temperature due to the action of the electric field may suggest the dominance of the electrostriction, increasing the radius of critical fluctuations whereas the opposite sign may be linked to the elongation of fluctuations leading to the decrease of the correlation length.…”

Interface initiation and propagation in liquid demixing with electric fields

“…Research on how electric fields affect phase transitions was motivated in recent decades by an interest in fundamental science, as well as by the potential for technological uses. [1][2][3][4][5][6][7][8] In non-conductive, non-polar liquids, however, spatially uniform electric fields minimally alter the mixingdemixing temperature. A uniform electric field E produces such small changes because the electrostatic energy stored per unit of molecular volume v of a liquid with dielectric constant ε is ∼ vεE 2 .…”