Formation and polarization of dipolar chains

Using polymer physics theory, we calculate the free energy difference of a single dipolar hard sphere chain and that of a dipolar fluid without chain structure at low density. The condition for the formation of a single dipol ar chain is derived. A dipolar chain will be formed only when the dipole mo ment is stronger than a threshold value. For a dipolar chain consisting of N dipoles, the total dipole moment distribution is calculated to be a Gauss ian function with finite-hi correction. For a system consisting of many mon odisperse dipolar chains, mean field calculations show that a phase transit ion occurs for sufficiently strong dipole strength or low enough temperatur e. The spontaneous polarization of the system and the critical dipole stren gth are also obtained. Furthermore, the chain length distribution function is obtained by the variational method. (C) 2000 Elsevier Science B.V. All r ights reserved.