Molecular theory of nematic liquid crystals viewed as effect of collective excitation in ferromagnetic systems
Liu Jian-Jun (刘建军)a, Shen Man (沈曼)a, Liu Xiao-Jing (刘晓静)a, Yang Guo-Chen (杨国琛)b
a College of Physics, Hebei Normal University, Shijiazhuang 050016, China; b Institute of Physics, Hebei University of Technology, Tianjin 300130, China
Abstract We develop a microscopic theory of the nematic phase with consideration of the effect of the collective excitation on properties of nematic liquid crystals. The model is based on the Heisenberg's exchange model of the ferromagnetic materials. Since the orientation of the molecular long axis and the angular momentum of the molecule rotating around its long axis have the same direction, operators can be introduced to research the nematic liquid crystals. Using the lattice model and the Holstein--Primakoff transformation, the Hamiltonian of the system can be obtained, which has the same form as that of the ferromagnetic substance. The relation between the order parameter and reduced temperature can be gotten. It is in good agreement with the experimental results in the low temperature region, the accordance is better than that of the molecular field theory and the computer simulation. In high temperature region close to the transition point, by considering the effect of the higher-order terms in the Hamiltonian, theoretical prediction is in better agreement with the experiment. That indicates the many-body effect is important to nematic liquid crystals.
Received: 08 April 2005
Revised: 26 May 2005
Accepted manuscript online:
PACS:
61.30.Cz
(Molecular and microscopic models and theories of liquid crystal structure)
Fund: Project supported by the Hebei Natural Science Foundation, China (Grant No A2004000140) and the Natural Science Foundation of Hebei Educational Committee, China (Grant No 2003107).
Cite this article:
Liu Jian-Jun (刘建军), Shen Man (沈曼), Liu Xiao-Jing (刘晓静), Yang Guo-Chen (杨国琛) Molecular theory of nematic liquid crystals viewed as effect of collective excitation in ferromagnetic systems 2006 Chinese Physics 15 163
Altmetric calculates a score based on the online attention an article receives. Each coloured thread in the circle represents a different type of online attention. The number in the centre is the Altmetric score. Social media and mainstream news media are the main sources that calculate the score. Reference managers such as Mendeley are also tracked but do not contribute to the score. Older articles often score higher because they have had more time to get noticed. To account for this, Altmetric has included the context data for other articles of a similar age.
