The decay of pair correlations in quantum hard-sphere fluids

Abstract

A study of the asymptotic decay of the pair radial correlations in the bare quantum hard-sphere (QHS) fluid and in the quantum hard-sphere Yukawa (QHSY) fluid is presented. The conditions explored are far from quantum exchange and are contained within the region (0.1<or=rho(N) (*)<or=0.8; 0.116 <or= lambda(B) (*)<or= 0.9). The three types of pair radial correlations existing in path-integral quantum monatomic fluids (instantaneous, pair linear response and centroids) are analyzed by utilizing the complex poles methodology expounded by Evans et al. [J. Chem. Phys. 100, 591 (1994); Phys. Rev. E 59, 1435 (1999)] complemented with Ornstein-Zernike frameworks appropriate for quantum fluids. Given that there is no analytical theory of the quantum direct correlation functions, the present applications rely on the short-ranged methodology of asymptotics augmented with increasing ranges of the cutoff. The following main issues of interest are addressed: the influence of the sample size on the decay properties, the features of the pole patterns arising from the asymptotic calculations, and the effect of Yukawa attractions on the decay properties of systems composed of quantum hard spheres. The results show that the decays in the QHS fluid are of the exponentially damped oscillatory type, and hence no indication of Fisher-Widom lines has been found. On the other hand, in the QHSY fluid, both pure exponential (monotonic) and exponentially damped oscillatory decays may be obtained. Consequently, there is evidence that Fisher-Widom lines can be expected for the three pair radial correlations in the QHSY fluid.

Path integral Monte Carlo study of quantum-hard sphere solids

“…[26][27][30][31][32][42][43][44][45][46][47][48][49] Some of them are of interest to this work: the accurate equation of state for the fluid phase reported recently, 49 a preliminary study of the fluid-solid fcc transition for intermediate densities, 31,32 and also the computation of a number of properties of the fcc and bcc lattices. 30 With the better computational means of today this article is devoted to extending and completing the foregoing QHS results by studying the properties of the fcc, hcp, and bcc solid phases.…”

On the accurate direct computation of the isothermal compressibility for normal quantum simple fluids: Application to quantum hard spheres

“…However, their exact decay properties are expected to be different, as suggested by the QHS dominant pole analysis reported in Ref. 39. These three functions should show exponentially oscillatory decay, but the period and inverse decay length of the CM oscillations should be smaller than those of the ET and the PLR cases.…”

“…One may mention, for instance, the general topic of the OZn equations 4,43,46 in which it is contained. This topic deals with quantum and classical static structure factors for fluids, 27,41,42,[46][47][48] the decay properties of the particle correlations, 39 interfacial phenomena, etc. 46(d) Besides, the study of complex molecular fluids that may be represented by spherically symmetric potentials (e.g.…”

“…The results so obtained were based on (N, V, T) simulations and showed excellent agreement with experiments and other theoretical approaches. [27][28][29][32][33][34][35][36][37][38][39][40][41][42] Clearly, there are other general methods to obtain isothermal compressibilities for quantum fluids, such as the evaluation of the fluctuations in the (µ, V, T)-number of particles 43,44 or in the (N, P, T)-volume. 43,15(b)- (c), 45 To carry out extensive grand ensemble simulations appears to be a daunting task in the quantum case.…”