STRUCTURE EVOLUTION, DIFFUSIVITY AND VISCOSITY OF BINARY AL-BASED AND NI-BASED METAL MELTS: AB INITIO MOLECULAR DYNAMICS STUDY
Open Access
Author:
Wang, Yi
Graduate Program:
Materials Science and Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 05, 2012
Committee Members:
Zi Kui Liu, Thesis Advisor/Co-Advisor
Keywords:
Diffusivity Viscosity Short rang order Bond pair Voronoi polyhedra
Abstract:
This thesis describes the structure evolution, diffusivity and viscosity of Al80Ni20, Al80Cu20, Al1-xZrx (x=0.4, 0.5. 0.6 and 0.67) and Ni1-xWx (x=0.1 and 0.2) melts through ab initio molecular dynamics (AIMD) at different temperatures, providing fundamental information in characterizing the glass formability.
The structure evolution is characterized in terms of pair correlation function, structure factor, coordinate numbers, Honeycutt-Anderson bond pair and Voronoi polyhedra. The short range ordering structures in the metal melts can be presented based on the analysis of Honeycutt-Anderson bond pair and Voronoi polyhedra. Self diffusivity and intrinsic diffusivity are calculated from the Einstein relation based on the mean square displacement of atoms. Viscosity is evaluated using Stock-Einstein relation derived for the motion of a macroscopic particle in a viscous medium. Our predicted pair correlation function, structure factor, diffusivity and viscosity are compared with available experimental data, such as high energy X-ray diffraction and quasielastic neutron scattering, showing favorable agreement.
