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Cu-Al and Pd-Ti system multi- body potential in the phase stability of Construction and research applications

Author: YangBin
Tutor: LaiWenSheng
School: Tsinghua University
Course: Materials Science and Engineering
Keywords: Molecular dynamics simulation First-principles calculations Many-body potential Glass-forming ability
CLC: O469
Type: Master's thesis
Year: 2009
Downloads: 82
Quote: 0
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Abstract


In recent decades, been developed a variety of non-equilibrium and preparation techniques have succeeded in obtaining a number of unique properties of non-equilibrium materials. Therefore, the development of materials science theories related to clarify the non-equilibrium microstructure of materials, preparation, and the correlation between the performance, materials science has become a major challenge faced. To this end, the field of materials science and condensed matter physics researchers made great efforts to develop the atomic interaction based on empirical potential molecular modeling and quantum mechanics starting from the electronic structure calculation methods, in order to be able to construct a new set of quantitative materials science theory. In molecular dynamics simulations, the simulation results depend on the reliability of many-body interatomic potential accuracy. For some there is no intermediate compounds or no data related to the physical properties of the alloy system, can not fit a real and effective interatomic many-body potential. In response to this difficulty, we used a first-principles auxiliary building multi-body potential approach. First, with first-principles calculation method for alloy systems that may exist in certain non-equilibrium phase relevant physical properties, and then through the fitting of these properties to determine the many-body potential in the specific values ??of the unknown parameters. Following this idea, we selected the generated heat is negative but the lack of data the intermediate phase Cu-Al and Pd-Ti system were constructed Tight-Binding forms of many-body potential. Fitting multi-body potentials can well reproduce the important physical properties of the system, indicating that the many-body potential in the reaction system can correct the interaction between atoms. In addition, based on multi-body potential molecular dynamics simulations of the system results in some of the problems are in good agreement with the experimental observations, both to further validate the resulting multi-body potentials fitting the true effectiveness is confirmed by first-principles auxiliary building multi-body potential feasibility of the method. In the Cu-Al system, we use the calculation to construct a multi-body FCC, BCC and amorphous solid solution of the energy changes with the solute atoms, by comparing the sequence of the three energy reveals Cu-Al binary system difficult obtained amorphous reasons: the energy of the solid solution is smaller than the amorphous phase, and calculations show that, BCC solid solution in the Al content is 32-72at.% range of the lowest energy, and the obtained composition range of the BCC solid solution single-phase Ball-milling experimental results. In the Pd-Ti system, we calculate FCC amorphous solid solution and the whole composition range order to obtain the energy range of the formation of amorphous 21-70at.% Pd, obtained in experiment 25-60at.% Pd match.

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