Thermodynamics of ferrofluids in applied magnetic fields / Elfimova Ekaterina A.,Ivanov Alexey O.,Camp Philip J. // PHYSICAL REVIEW E. - 2013. - V. 88, l. 4.

ISSN/EISSN:

1539-3755 / 1550-2376

Type:

Article

Abstract:

The thermodynamic properties of ferrofluids in applied magnetic fields are examined using theory and computer simulation. The dipolar hard sphere model is used. The second and third virial coefficients (B-2 and B-3) are evaluated as functions of the dipolar coupling constant lambda, and the Langevin parameter alpha. The formula for B-3 for a system in an applied field is different from that in the zero-field case, and a derivation is presented. The formulas are compared to results from Mayer-sampling calculations, and the trends with increasing lambda and alpha are examined. Very good agreement between theory and computation is demonstrated for the realistic values lambda <= 2. The analytical formulas for the virial coefficients are incorporated in to various forms of virial expansion, designed to minimize the effects of truncation. The theoretical results for the equation of state are compared against results from Monte Carlo simulations. In all cases, the so-called logarithmic free energy theory is seen to be superior. In this theory, the virial expansion of the Helmholtz free energy is re-summed in to a logarithmic function. Its success is due to the approximate representation of high-order terms in the virial expansion, while retaining the exact low-concentration behavior. The theory also yields the magnetization, and a comparison with simulation results and a competing modified mean-field theory shows excellent agreement. Finally, the putative field-dependent critical parameters for the condensation transition are obtained and compared against existing simulation results for the Stockmayer fluid. Dipolar hard spheres do not undergo the transition, but the presence of isotropic attractions, as in the Stockmayer fluid, gives rise to condensation even in zero field. A comparison of the relative changes in critical parameters with increasing field strength shows excellent agreement between theory and simulation, showing that the theoretical treatment of the dipolar interactions is robust.

Author keywords:

DIPOLAR HARD-SPHERES; LIQUID-VAPOR COEXISTENCE; SIMPLE POLAR FLUIDS; CRITICAL-TEMPERATURE; ORIENTATIONAL ORDER; PERTURBATION-THEORY; COMPUTER-SIMULATIONS; VIRIAL-COEFFICIENT; PHASE; TRANSITION

DOI:

10.1103/PhysRevE.88.042310

Web of Science ID:

ISI:000326118200005

Соавторы в МНС:

Другие поля

Поле	Значение
Month	OCT 23
Publisher	AMER PHYSICAL SOC
Address	ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Language	English
Article-Number	042310
EISSN	1550-2376
Keywords-Plus	DIPOLAR HARD-SPHERES; LIQUID-VAPOR COEXISTENCE; SIMPLE POLAR FLUIDS; CRITICAL-TEMPERATURE; ORIENTATIONAL ORDER; PERTURBATION-THEORY; COMPUTER-SIMULATIONS; VIRIAL-COEFFICIENT; PHASE; TRANSITION
Research-Areas	Physics
Web-of-Science-Categories	Physics, Fluids \& Plasmas; Physics, Mathematical
Author-Email	philip.camp@ed.ac.uk
ResearcherID-Numbers	Ivanov, Alexey/E-4442-2011 Elfimova, Ekaterina/P-5003-2016
ORCID-Numbers	Ivanov, Alexey/0000-0001-8239-4039 Elfimova, Ekaterian/0000-0002-8941-8184 Camp, Philip/0000-0002-7901-1364
Funding-Acknowledgement	Ministry of Education and Science of the Russian Federation {[}N2.609.2011]; Russian Foundation for Basic Research {[}N12-02-31079, N13-02-91052-CNRS-a]
Funding-Text	E.A.E. and A.O.I. gratefully acknowledge grants from the Ministry of Education and Science of the Russian Federation (N2.609.2011) and the Russian Foundation for Basic Research (N12-02-31079, N13-02-91052-CNRS-a). E. A. E. and P.J.C. thank the Ural Federal University for supporting collaborative visits between Edinburgh and Ekaterinburg.
Number-of-Cited-References	69
Usage-Count-Last-180-days	2
Usage-Count-Since-2013	25
Journal-ISO	Phys. Rev. E
Doc-Delivery-Number	240SV