Atomistic study of phase transitions / Alex M. Nieves.

Format:

Book

Manuscript

Thesis/Dissertation

Author/Creator:

Nieves, Alex M.

Contributor:

Sinno, Talid, advisor.

Vitek, V., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Chemical and biomolecular engineering.

Chemical and biomolecular engineering--Penn dissertations.

Local Subjects:

Penn dissertations--Chemical and biomolecular engineering.

Chemical and biomolecular engineering--Penn dissertations.

Physical Description:

xi, 157 pages : illustrations (some color) ; 29 cm

Production:

2011.

Summary:

Two theoretical studies of phase transitions are presented in this thesis. The first topic explores the capacity to modulate compositional patterning during phase segregation in a binary alloy using applied strain fields. A quasi-static Metropolis Monte Carlo algorithm is developed to study the effects of strain in the atomic diffusion process. Using different parameterizations of the binary Lennard-Jones model, a set of guidelines for material selection and ideal process conditions are generated. Our results from the Lennard Jones model are compared with those from a MEAM parameterization of the Cu-Ni alloy and the EAM parameterization of the Cu-Al alloy. The second topic focuses in using the inherent structure framework to provide an energy landscape description of the homogeneous and heterogeneous melting process. The inherent structure theory is derived for the NVT and NPT ensembles. First the effects of pressure in homogeneous melting are studied on silicon and aluminum systems. The homogeneous melting mechanism is driven by the formation of interstitial-vacancy (I-V) complexes, and it is found that the slope of the density-of-state (DOS) curve, gives a direct measurement of the homogeneous melting temperature of the system. It is also found that the melting temperature is affected by the formation volume of these I-V defects. Finally a DOS analysis of melting under three heterogeneous systems with different degrees of curvatures: planar surface (zero curvature), nanoparticle (positive curvature), and internal cavity (negative curvature), is given. It is found that the shape of the DOS curve gives the melting temperature of the heterogeneous feature and it also contains information about underlying mechanism of solid-liquid interactions. We propose a model based in the curvature of the defect and the DOS penalty of for a liquid in contact with the solid that can gives new insight into the contributions of underlying basin distribution in the energy landscape to the melting mechanism of these systems.

Notes:

Advisers: Talid Sinno; Vaclav Vitek.

Thesis (Ph.D. in Chemical and Biomolecular Engineering) -- University of Pennsylvania, 2011.

Includes bibliographical references.