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Simulated Annealing Model and Martensitic Transformation

模拟退火模型和马氏体转变

基本信息

批准号：
63540261
负责人：
AKAI Hisazumi
金额：
$ 1.28万
依托单位：
Nara Medical University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

项目摘要

The purpose of the present project was, partly, to develop the ab-initio molecular dynamics (MD) method, which had been so successful for semi-conductor physics, such that it was also applicable to transition metal systems. Though not yet having got the molecular dynamics actually run, the project, we believe, is really successful in the sense that we could make a steady step to this end. Since the above MD method had not been completed, we were obliged, in studying martensitic transformations, which itself formed another part of the present project, to use rather conventional methods : one based on a phenomenological approach, another by electronic structure calculations. New developments which have been made so far concerning the project are summarized in the following :i) We have established the full-potential KKR method as a realistic and convenient tool for accurate electronic structure calculation of metallic and complex systems. It was shown that this new technique was applicabl … More e to the simulated annealing model, or the molecular dynamics, rather straightforwardly, and thus enabled us to perform a Car-Parrinello-like Procedure also for transition metals. Our preliminary calculations showed that dealing with an unit cell containing-10 atoms in it by this method would cost around 1 minute of CPU time on a typical super-computer.ii) Relation between periods of spatially modulated first-kind antiferromagnetic structure and orthorhombic lattice distortion in an fcc lattice were discussed on a basis of Landau's phenomenological theory. The period of the magnetic modulation turned out either the same or twice as long as that of the lattice distortion. The magnetic structure of gamma-Fe precipitated in Cu was discussed in the light of this result.iii) To reveal the microscopic origin of the successive martensitic transformation seen in Fe-Pd system near Pd 30% region, we performed the KKR-CPA-LSD electronic structure calculation. The total energy change was calculated accurately along the pass connecting the fcc and bcc structures (Bain's distortion). The result showed that the fcc structure actually became unstable around Pd 30%. The calculation, however, failed to prove the existence of the fct phase, which is likely to exist experimentally even at T=OK ; instead it predicted a 1st order-like jump from the fcc to the bcc structure. Less

本项目的部分目的是发展从头算分子动力学方法，这种方法在半导体物理学方面非常成功，因此也适用于过渡金属系统。虽然还没有真正运行分子动力学，但我们相信，这个项目是非常成功的，因为我们可以朝着这个目标稳步前进。由于上述MD方法尚未完成，我们不得不在研究马氏体相变时使用相当传统的方法：一种基于唯象方法，另一种基于电子结构计算。马氏体相变本身也是本项目的另一部分。本文综述了迄今为止该项目的新进展：（1）我们建立了全势KKR方法，作为精确计算金属和复杂体系电子结构的一种现实而方便的工具。结果表明，该技术是可行的。 ...更多信息 e的模拟退火模型，或分子动力学，而直接，从而使我们能够执行的Car-Parrinello-like程序也过渡金属。我们的初步计算表明，用这种方法处理一个含有~10个原子的单胞，在一台典型的超级计算机上大约需要1分钟的CPU时间。ii）在朗道唯象理论的基础上，讨论了面心立方晶格中第一类反铁磁结构空间调制周期与正交晶格畸变之间的关系。磁调制的周期与晶格畸变的周期相同或两倍长。为了揭示Fe-Pd系中Pd30%附近连续马氏体相变的微观起源，我们进行了KKR-CPA-LSD电子结构计算。沿着连接面心立方和体心立方结构的孔型精确计算总能量变化（贝恩畸变）。结果表明，fcc结构实际上在Pd 30%附近变得不稳定。然而，该计算未能证明fct相的存在，即使在T = OK时也可能存在;相反，它预测了从fcc到bcc结构的一阶跳跃。少