Simulation estimates of cloud points of polydisperse fluids.

نویسندگان

  • Matteo Buzzacchi
  • Peter Sollich
  • Nigel B Wilding
  • Marcus Müller
چکیده

We describe two distinct approaches to obtaining the cloud-point densities and coexistence properties of polydisperse fluid mixtures by Monte Carlo simulation within the grand-canonical ensemble. The first method determines the chemical potential distribution mu(sigma) (with the polydisperse attribute) under the constraint that the ensemble average of the particle density distribution rho(sigma) match a prescribed parent form. Within the region of phase coexistence (delineated by the cloud curve) this leads to a distribution of the fluctuating overall particle density n, p(n), that necessarily has unequal peak weights in order to satisfy a generalized lever rule. A theoretical analysis shows that as a consequence, finite-size corrections to estimates of coexistence properties are power laws in the system size. The second method assigns mu(sigma) such that an equal-peak-weight criterion is satisfied for p(n) for all points within the coexistence region. However, since equal volumes of the coexisting phases cannot satisfy the lever rule for the prescribed parent, their relative contributions must be weighted appropriately when determining mu(sigma). We show how to ascertain the requisite weight factor operationally. A theoretical analysis of the second method suggests that it leads to finite-size corrections to estimates of coexistence properties which are exponentially small in the system size. The scaling predictions for both methods are tested via Monte Carlo simulations of a polydisperse lattice-gas model near its cloud curve, the results showing excellent quantitative agreement with the theory.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Finite-size scaling and particle-size cutoff effects in phase-separating polydisperse fluids.

We study the liquid-vapor phase behavior of a polydisperse fluid using grand canonical simulations and moment free energy calculations. The strongly nonlinear variation of the fractional volume of liquid across the coexistence region prevents naive extrapolation from detecting the cloud point. We describe a finite-size scaling method which, nevertheless, permits accurate determination of cloud ...

متن کامل

Wetting transitions in polydisperse fluids.

The properties of the coexisting bulk gas and liquid phases of a polydisperse fluid depend not only on the prevailing temperature but also on the overall parent density. As a result, a polydisperse fluid near a wall will exhibit density-driven wetting transitions inside the coexistence region. We propose a likely topology for the wetting phase diagram, which we test using Monte Carlo simulation...

متن کامل

Optimal packing of polydisperse hard-sphere fluids II

We consider the consequences of keeping the total surface fixed for a polydisperse system of N hard spheres. In contrast with a similar model (J. Zhang et al., J. Chem. Phys. 110, 5318 (1999)), the Percus-Yevick and Mansoori equations of state work very well and do not show a breakdown . For high pressures Monte Carlo simulation we show three mechanically stable polydisperse crystals with eithe...

متن کامل

Phase coexistence in polydisperse mixture of hard-sphere colloidal and flexible chain particles

Abstract. A theoretical scheme for the calculation of the full phase diagram (including cloud and shadow curves, binodals and distribution functions of the coexisting phases) for colloidpolymer mixtures with polymer chain length polydispersity and hard-sphere colloidal and polymeric monomer sizes polydispersity is proposed. The scheme combines thermodynamic perturbation theory for associating f...

متن کامل

Melting of polydisperse colloidal crystals in nonequilibrium.

The influence of a time-dependent oscillatory external field on the melting transition of a polydisperse colloidal crystal is examined by theory and computer simulation. In a monodisperse crystal the field just induces an overall dynamical mode which does not affect the melting line. For a polydisperse sample, on the other hand, the field shifts the melting line towards smaller temperatures. Co...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Physical review. E, Statistical, nonlinear, and soft matter physics

دوره 73 4 Pt 2  شماره 

صفحات  -

تاریخ انتشار 2006