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DENSITY FUNCTIONAL STUDY OF CLASSICAL LIQUIDS

by VALERA, MANUEL ANTONIO

Abstract (Summary)
A study of the freezing properties of simple liquids composed of hard and soft spheres is performed using classical density functional theory (DFT). The systems studied are composed of single component and binary mixtures. The behavior of binary mixtures as a function of the size ratio is analyzed. DFT equations are solved using an enhanced numerical method, which is based on a real-space mesh that does not constrain the shape of the density. Fast Fourier transforms are used to produce solutions efficiently. The reliability of the method is studied as a function of the mesh size in order to find an optimal implementation. A comparison with the exact known molecular dynamics result for single component systems shows excellent agreement. The solutions for binary mixtures of hard spheres reveal a qualitatively different behavior from previous results obtained using plane waves and gaussian parametrization. An fcc structure is found for almost identical particles, size ratio ~ 1:1. As the size ratio is reduced, a "sublattice-melt" phase is found with the small particles having a nonlocalized density and a multiple peak structure. Finally, the system reaches a NaCl structure at a size ratio of (0.45:1), with well-localized peaks in the density for small and large particles. For the same range of size ratios, the study of soft spheres mixtures reveals a similar behavior with the existence of non-stable solutions for size ratios of (0.80:1). Calculations on ternary systems were performed and the existence of the critical polydispersivity was found, which suggest similarities to real polydisperse systems.
Bibliographical Information:

Advisor:

School:University of Cincinnati

School Location:USA - Ohio

Source Type:Master's Thesis

Keywords:density functional theory simple liquids hard spheres glasses soft

ISBN:

Date of Publication:01/01/2002

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