Resolving the structural relaxation of a two-dimensional liquid using apertured cross correlation functions

Time-delayed intensity cross correlation functions are used to analyze the structural relaxation of a two-dimensional liquid of soft disks as simulated using a molecular dynamics algorithm. The structural relaxation exhibits an increasing long time tail as the freezing transition is approached. A cross correlation function designed to select out only local hexagonal fluctuations is used to demonstrate explicitly that this slow relaxation arises from crystalline fluctuations. A theoretical treatment of the role of aperture size and cluster distribution in the scattering correlation functions is presented.