Abstract
The partition function of a system with pairwiseadditive anisotropic dipoledipole interactions is equal to that of a hypothetical system with manybody isotropic interactions [G. Stell, Phys. Rev. Lett. 32, 286 (1974)]. The effective manybody interactions contain nbody contributions of all orders. Each contribution is known as an expansion in terms of the particleparticle distances r, and the coefficients are temperature dependent. The leadingorder twobody term is the familiar r(6) attraction, and the leadingorder threebody term is equivalent to the AxilrodTeller interaction. In this work, a fluid of particles with the leadingorder twobody and threebody interactions is compared to an equivalent dipolar softsphere fluid. Molecular simulations are used to determine the conditions under which the effective manybody interactions reproduce the fluidphase structures of the dipolar system. The effective manybody interaction works well at moderately high temperatures but fails at low temperatures where particle chaining is expected to occur. It is shown that an adjustment of the coefficients of the twobody and threebody terms leads to a good description of the structure of the dipolar fluid even in the chaining regime, due primarily to the groundstate linear configuration of the threebody AxilrodTeller interaction. The vaporliquid phase diagrams of systems with different AxilrodTeller contributions are determined. As the strength of the threebody interaction is increased, the critical temperature and density both decrease and disappear completely above a threshold strength, where chaining eventually suppresses the condensation transition. (C) 2015 AIP Publishing LLC.
Original language  English 

Article number  024501 
Number of pages  10 
Journal  The Journal of Chemical Physics 
Volume  143 
Issue number  2 
DOIs  
Publication status  Published  14 Jul 2015 
Keywords
 LIQUID PHASE COEXISTENCE
 HARDSPHERES
 MONTECARLO
 ORIENTATIONAL ORDER
 CRITICALBEHAVIOR
 POLAR FLUIDS
 PAIR
 VAPOR
 POTENTIALS
 FERROFLUIDS
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Simulations of dipolar fluids using effective manybody isotropic interactions
Camp, P. (Creator), Edinburgh DataShare, 1 Jul 2015
DOI: 10.7488/ds/276
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