Single Chain Formation and Spontaneous Polarization in Dipolar Chain Systems

Jiun-Yan Huang；Pik-Yin Lai

Chinese Journal of Physics

38卷5期（2000 / 10 / 01）

962 - 974

英文

Dipolar fluids can form chain structures at low density provided the dipole moments are strong enough. Using polymer physics theory, we calculate the free energies of a single dipolar hard sphere chain and for a dipolar fluid without chain structure at low density. The condition for the formation of a single dipolar chain is derived. A dipolar chain will be formed only when the dipole moment is stronger than a threshold value. For a dipolar chain consisting of N dipoles, the total dipole moment distribution is calculated to be a Gaussian function with finite-N correction. The segment correlation length, the average size of the dipole chain as a function of the dipole strength, are calculated. For a system consisting of many monodisperse dipolar chains, mean field calculations show that a phase transition occurs for sufficiently strong dipole strength or low enough temperature. The spontaneous polarization of the system and the critical dipole strength are also obtained. Furthermore, the chain length distribution function is obtained by the variational method.