Mixed picture for quantum system and the effects of high strain-rate on mechanical behavior of gold nanowires

• Main Authors: Dao-Long Chen, 陳道隆
• Other Authors: Tei-Chen Chen
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/03017698741651874612

博士 === 國立成功大學 === 機械工程學系碩博士班 === 94 === 　The mixed picture is introduced to represent electronic-nucli quantum system. The Schrdinger-like equations can be obtained for electrons, and the wave function can be habitually used for the motion of electrons. On the other hand, the Heisenberg-like equations of motion can be obtained for nuclei and are analogous to classical mechanics. The mixed picture can be applied to the quantum statistical mechanics and can be conveniently used to derive the equations of motion of the mixed quantum-classical system. The proof is also derived that under canonical ensemble, the isothermal molecular dynamics should be combined with the canonical time-dependent density-functional theory instead of microcanonical one which was used by a reference. The effects of high strain-rate on mechanical behavior of gold nanowire are studied under different temperatures and different crystalline orientations. The properties are focused such as the distributions of stresses, the changes of cross sections, the evolutions and distributions of radial distribution functions, stress-strain and energy-strain relations, maximum strengths, and Young’s moduli. The common neighbor analysis is used to study the changes of local structures and the corresponding relations to stresses and energies. The maximum strengths and Young's moduli are also related to strain-rates. According to the smooth changes of local structures and mechanical properties, we predict that the quantized conductivities, which occur under lower strain-rate, will not be observed under high strain-rate.