Determination of orientational distribution function of organic molecular surfaces using the modified maximum-entropy method

摘要

The determination of the surface orientational distribution function for organic molecules such as liquid crystals has been studied using the maximum-entropy method with second-order optical nonlinear coefficients. Systematic simulation revealed that the conventional maximum-entropy method does not give sufficient information about the axial ordering ([cos(2)theta]) along the surface normal direction (theta is the angle between the molecular axis and surface normal direction). We propose a modified maximum-entropy method that involves an additional constraint function of [cos(2)theta] and gives more realistic distribution functions. Distribution functions were determined for several previous experimental results using these conventional and modified methods. From the comparison of these distribution functions, it has been shown that the distribution densities of` molecules oriented at tilt angle theta=180 degrees, which appear when using the conventional maximum-entropy method, are artifacts. [References: 25]