Nonequilibrium-molecular-dynamics investigation of the presmectic behavior of the viscosities of a Gay-Berne nematic-liquid crystal

Using the method of nonequilibrium molecular dynamics, the behavior of the Miesowicz, Helfrich, and Leslie viscosities as functions of temperature and density are investigated. In particular, attention is focused on the region immediately preceding the nematic-smectic phase transition. The Miesowicz viscosity eta(1) for the orientation parallel to the direction of flow and the Helfrich viscosity eta(12) are both found to increase rapidly as the phase transition is approached. In most of the cases investigated, a critical exponent nu=1/3 is found. Values closer to nu= 1/4 are also found, but in these cases, the errors are sufficiently large for y=1/3 to be possible. No nonregular behavior of the viscosity coefficients eta(2), eta(3), gamma(1), and gamma(2) in the presmectic region was detected. [S1063-651X(99)01710-9].