5 20 30 40 50 r$_{s}$  (a.u.) 0.808 0.810 0.812 0.814 0.816 0.818 0.820 ( E  + 1.106103/ r$^{s}$  )  r$^{s}$ 3/2  (a.u.) Ferro. crystal Antif. crystal Ferro. fluid Para. fluid FIG. 1: (Color online) DMC energy as a function of $^{r}$s for ferromagnetic and antiferromagnetic triangular Wigner crystals and paramagnetic and fully ferromagnetic Fermi fluids. In each case the Madelung energy of a triangular crystal has been subtracted from the energy and the result has been rescaled by r 3 / 2 s to highlight the differences between the curves. An experimental result for the crystallization density is r$_{s}$ = 35 . 1(9) a.u. [29], which is somewhat lower than the QMC crystallization density. This suggests that the ideal 2D HEG is not a perfect model for electron layers in real semiconductor devices. It has been argued that the transition from a 2D Fermi fluid to a Wigner crystal cannot be first order, because, at the transition density, it is energetically favorable to create boundaries between macroscopically separated regions of fluid and crystal [8]. The energy of the Bose fluid is substantially lower than that of the Fermi fluid in the vicinity of the crystallization density in 2D, unlike 3D [30]. There is therefore more scope for interesting phase behavior in 2D. Various intermediate phases have been proposed in the literature, such as a hexatic phase with orientational but not translational order [9], a supersolid phase [10], or a microemulsion phase [8]. Falakshahi and Waintal [11] have suggested that a “hybrid” phase is stable in the vicinity of the transition density from a ferromagnetic fluid to a ferromagnetic Wigner crystal. (We have found that a paramagnetic fluid is stable at this density; however, we