Hard-particle model systems help to improve our understanding of the effect of particle shape on collective behavior at a fundamental level. Furthermore, these system can now be realized in the form of colloids or nanoparticles due to recent advances in synthesis techniques [1]. A driving force for these efforts is the possibility that these experimental systems form structures that can be applied as novel materials. While these hard-particle systems were originally studied using computer simulations [2], the application of continuum theories is more natural for some long-wave-length or high-symmetry problems.Density functional theory (DFT) [3,4] is a continuum theory for systems that are inhomogeneous or anisotropic either due to applied external fields [3,5,6] or spontaneous symmetry breaking [7][8][9]. Hard spheres represent a classical and quite tractable system to which density functional theory has been applied in many studies. One of the most successful versions of DFT for hard-sphere mixtures is Rosenfeld's fundamental measure theory (FMT), which is based on the fundamental measures of each spherical component, namely, its radius, area and volume [10]. A version of FMT derived from the zero-dimensional limit [11,12] has proven to be very successful in predicting the properties of the crystal [8]. This FMT has been further modified to yield the excellent Carnahan-Starling equation of state [13] for the homogeneous fluid and the resulting FMT [14,15] predicts the hard-sphere freezing transition very accurately [16].Simultaneously, the interest in liquid crystals has been a motivation to apply DFT to anisotropic particles, for instance, hard spherocylinders, idealized rod-like molecules. The isotropic-smectic-A and nematic-smectic-A phase transitions of these rods were determined using different weighted density versions of DFT for anisotropic particles [17][18][19][20] and showed reasonable agreement with the essentially exact simulation results of [21]. However, the construction of the free energy functional of these theories is ad hoc and we would like to use a functional based solely on the geometry of the particles, such as FMT for hard spheres. Some fundamental
AbstractDensity functional theory (DFT) for hard bodies provides a theoretical description of the effect of particle shape on inhomogeneous fluids. We present improvements of the DFT framework fundamental measure theory (FMT) for hard bodies and validate these improvements for hard spherocylinders. To keep the paper self-contained, we first discuss the recent advances in FMT for hard bodies that lead to the introduction of fundamental mixed measure theory (FMMT) in our previous paper (2015 Europhys. Lett. 109 26003). Subsequently, we provide an efficient semi-empirical alternative to FMMT and show that the phase diagram for spherocylinders is described with similar accuracy in both versions of the theory. Finally, we present a semiempirical modification of FMMT whose predictions for the phase diagram for spherocylinders are in excellent quanti...