Computational study of the melting-freezing transition in the quantum hard-sphere system for intermediate densities. II. Structural features.

The structural features of the quantum hard-sphere system in the region of the fluid-face-centered-cubic-solid transition, for reduced number densities 0.45<rhoN*<or=0.9 (reduced de Broglie wavelengths lambdaB*<or=0.8), are presented. The parameters obtained with path-integral Monte Carlo simulations for the fluid, amorphous, and solid phases are related to the distinct sorts of pair correlations that can be defined in a path-integral quantum fluid (instantaneous, continuous linear response and centroids). These parameters cover the pair radial correlation functions, the configurational structure factors, the order parameters Q4 and Q6, and the radii of gyration of the path-integral necklaces. Also, the fluid static structure factors have been computed by solving appropriate Ornstein-Zernike equations. A number of significant regularities in the above parameters involving both sides of the crystallization line are reported, and a comparison with results for Lennard-Jones quantum systems that can be found in the literature is made. On the other hand, the main amplitudes of the quantum fluid structure factors follow a complex behavior along the crystallization line, which points to difficulties in identifying a neat rule, similar to that of Hansen-Verlet for classical fluids, for these quantum amplitudes. To complete this study a further analysis of the instantaneous and centroid triplet correlations in the vicinities of the fluid-face-centered-cubic-solid phase transition of hard spheres has been performed, and some interesting differences between the classical and quantum melting-freezing transition are observed.